SD 



TIMBER PHYSICS. 



RESUME OF mA^ESTIGATIONS CARRIED OiN IS THE 
U. S. DIVISION OF FORESTRY, 



1889 TO 1898. 



By FTLTl^EKT TtOTH, 

ASSISTANT FKOFESSOK, SEW TOJCE .STATi; COhLEUE OF FOBESTJiS, CORNELL VNlVEliSITY. 



Repiiiitf-a from H. Doc. No. 181, o3th Cong., 3d Sess. 



WASHINGTON: 

GOVERNMENT PRINTING OFFICE. 
1899. 







Book 



// 



TIMBER PHYSICS 



RESUME OF INVESTIGATIONS CARRIED ON IN THE 
U. S. DIVISION OF FORESTRY, 



1889 TO 1898. 



By FILTBERT ROTH, 

ASSISTAXT rlCOFESHOK, liE^\^ YOllK STATE COLLEUE OF FOIlEHTIiY, CORNELL I.VJVEJiSITr. 



Reprinted from H. Doc. No. 181, 5.jth Cong., :!(1 Sess. 



WASHINGTON: 

GOVERNMENT PRINTING OFFICE. 

1899. 



^'^ 

•<^'^ 

^^^*^ 



Tin; WORK IX TIMBI'R PIIVSICS IN THE DIVISION OF 

FORI'STK\. 



liv Fii.iiiERr RoTii, 
J^ale Asaisltuit in Ihr Dii'ision of Vorfstry, 



HlS'J'OKKUL. 



As in the case of other materials, exact investigation of tlie properties of wood did not begin 
until the latter i)art of the eighteenth and the beginning of tlie nineteenth century, when Girard 
Buffon and Duhaniel du Moncean in France, and Petcu- Barlow, the nestor of engineering in 
England, laid tlie foundation for tliis inquiry by devisiug suitable methods and working out 
correct formula' for the computation of the results. As might be expected, the results of this 
pioneer work, particularly that of the French investigators, were often contradictory, and have 
to-day little more than historical value. 

Subsecpiently our knowledge of wood in general, and that of European species in partienlai', 
was increased by a number of experimenters. Among these, Ohevandier and Wertheim in France, 
and Niirdlinger in (Germany, stand out conspicuous. Unfortunatelj', their apjiaratus was ci'ude 
and, in the ease of the French workers, the series was too small to satisfy so complicated a 
problem, while Nordlinger was obliged to content himself with small and few specimens, owing to 
a want of i)roper equii)ment. 

In England considerable money was expended from time to time both by Government and 
private enterprise, but tlie eagerness of making the matter as practicable as possible led, unfortu- 
nately, to much testing of large sizes and to the employment of insufficient (because unsystematic) 
metliods, so that such extreme exi)erinients as those of Fowke and others have really neither 
furthered science nor heli)ed the practice. In this country the engineering world for a long time 
relied largely on the results of Furoi)ean testing, and the wood consumers in general depended 
on a meager accumulation of experience and crude observation concerning most of tlie line array 
of valuable and abundant kinds of timber offered in our markets. 

Ignorance and prejudice had their way. Chestnut oak was pronounced uuiit for railway ties, 
and thus millions of logs were left rotting in the M'oods, though this prejudice had not a single 
fair trial to supjiort it. "Bled"' lougleaf, or (ieorgia pine, was considered weaker and less durable, 
millers and dealers were obliged to misrepresent their goods, causing unnecessary loss and litiga- 
tion, and yet there existed not a single record of a properly conducted experiment to substantiate 
these views. Gum was of no value. Southern oak was publicly i)roclaimed as unfit for carriage 
builders, and the ^■iews as to the usefulness of different timbers were almost as numerous as the 
men expounding them. 

The engineering world was the first to realize this deficiency, and men like Hatfield, Lanza, 
Thurston, and others attempted to replace the few anti(iuated and unreliable tables of older text- 
books by the results jierforined on American woods and with modern aiqjiiances. 

In addition to these efforts of engineers, Sharpies, under Sargent's direction, in his great 
work for the Tenth Census of ISSO, subjected samples of all oui' timber trees to mechanical tests, 
but, since in these tests only a few select pieces represented each species, tlie engineering world 
never ventured to use the results. As regards the rest of the wood testing in our country, it may 
be said that it generally possessed two serious defects: (1) the wood was not properly chosen, and 
(2) the methods of testing were defec^tive, especially witli respect to the various states of seasoning, 
wood being tested in almost every state from green to dry, without distinction. This is the more 
330 



AKi 17 1906 



TIMBER PHYSICS. 



331 



remarkable since the important intlnence of inoistnre was recognized and emphasized by both 
French and (lerman experimenters more than forty years ago.' 

These facts were fully appreciated by the engineers of our country, as is well shown by the 
numerous, often emphatic, approvals and recommendations of the timber-physics work undertaken 
by the Division of Forestry, and by the eagerness with which wood consumers generally seized on 
all information of this kind as fast as the Division of Forestry could supply the same. 

SOUTHEUN AND N^ORTHBRN OAK. 

Though fully planned before, the work in timber physics was really begun in order to decide 
an important controversy as to the relative value of Southern and Northern grown oak. 

A representative committee of the Carriage Builders' Association had publicly declared that 
this important industry could not depend upon the supplies of Southern timber, as the oak grown in 
the South lacked the necessary qualities demanded in carriage construction. Without experiment 
this statement could be little better than a guess,^ and was doubly unwarranted, since it condemned 
an enormous amount of material, and one produced under a great variety of conditions and by at 
least a dozen ditterent species of trees, involving, therefore, a complexity of problems dithcult 
enou-h for the careful investigator, and entirely beyond the few unsystematic observations ot the 
members of a committee on a flying trip through one of the greatest timber regions of the world 

A number of samples were at once collected (part of them supplied by the carriage builders 
committee) and the fallacy of the broad statement mentioned was fully demonstrated by a short 
series of tests and a more extensive study into structure and weight of these materials. From 
the.se tests it appears that pieces of white oak from Arkansas excelled well-selected pieces from 
Connecticut both in stiffness and endwise compression (the two most important forms of resistance). 

Besults oftfsU on NoHhen, and Sonthem white oak made in Wmhinglon University Laboraton,, St. Lewis, Mo., h, I'rof. 

J. B. Johnson, 1SS9. 







BeudiDS and cross breaking. Size of test piece 1% by 
1| by 24. 


Compression. 


Shearing. 


Test piece. 


Stiffness. 


Ultiraate 
strength. 


Resistance to 
shock. 


Endwise. 


Transverse. 


Longitudinal. 


Where procured. 


No. 


Range 

No. 


SMoilalus 1 
of elas- 
ticity, 
ponuda 

per 
sqnare 
inch. 


Range 
No. 


Modulus 
3. W. L. 
2. b. h' 
pounds 

per 
square 
inch. 


Range 
No. 


Modulus 

'"t^^: 1 Range 
pounds . jj„s 

per cubic 

inch, j 


Modulus 
ponnda 

per 

square 

inch. 

Size 1| by 

5 inches. 


Range 
No. 


I 
Modulus 
pounds ' 

per 
square 
inch. 


Range 
No. 


Modulus 
pounds 

per 

squan^ 

inch. 


A. a. I 


1 
2 


9 
5 


99(1. 000 
1, 280, IIOO 


3 

1 


13,700 
18.50;) 


4 
1 


1 
59 [ 
92 7 


6,160 
5,48U 


1 
3 


3, 400 3 
3, 100 1 


1,375 
1, 500 


Average 


3 1 1.135,000 


1 


16, 130 1 


76 


3 


5, 820 


1 


3,230 j 1 1,468 


A.b. II 


3 

4 




6 1,120,000 
10 920,000 


8 
5 


12. 3U0 
12, 700 


6 


47 
55 


11 
i) 


4,740 
4,980 


7 

4 


2,500 
2, 800 


C 

7 


i,'325 


Average 


4 1 1, 020, 000 


3 


12, 500 1 3 


51 


5 


4, 860 


2 


2, 650 


3 1 1.225 




5 
6 


11 1 850,000 
7 1 1, 140, 000 


9 


11,400 1 2 
12,300 7 


83 
45 


8 
10 


5, 230 
4,820 


5 
8 


2,700 
2,500 


4 1 1,375 
2 1 1.540 




5 \ 995,000 1 6 


11,860 2 


64 


4 


5,025 


3 


2,600 


2 


1,4S8 






1 








B 




Size: 1| by I j by 18 inches. 


Size: Ig cube. 






_. ^ ; 




7 
8 
9 


3 1.570,000 

8 1, 100, 000 

4 1,385,000 


6 12,380 
2 14, 690 
11 11, 240 


9 
3 
11 


27 
82 
19 


4 

1 
5 


6,800 
7,800 
6,800 


11 
2 
9 


2,000 
3,200 
2,300 


10 
5 
11 


' 860 

1, 260 

825 


Average 


2 1 1,351,667 


2 12, 770 


4 


43 


2 


7,133 4 


2, 500 1 5 


982 




10 
11 


1 j 1,653,000 

2 i 1,581,000 


4 
10 


13, 030 
11, 590 


8 
10 


30 
22 


3 
2 


6,900 1 6 
7,700 10 


2,000 
2,100 


i 8 
9 


1,050 
940 




1 1.617,001) 


4 


12, 310 


5 


26 


] 


7,300 j 5 


2,350 


4 1 995 










1 



















) For a more complete history see Bulletin 6 of Division of Forestry. 
2 See Report of the Division of Forestry, 1890, page 209. 

fW. = total load al center in i)ound3 
W L 3 where ^- =^ length in juclus. 
.youn-s ,„odulus of elasticity: ^^^r^;^, IJ; Z^^^!^^:^' 

\^. = l)eii;lit in inches. 



332 



FOKESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGKICULTUKE. 



Ih-iicriiition of li'f<t materiuf and n-nults of pht/aicat examination. 



>fotatioD as to statioq, »ite, ami tree ! A. a. I. CouBecti- [ 

cut upland. ' 

NunilHT of test piece ] . 

Kxp«9Uie iu tree Nortli. 

Heij,'Iit in Ireu i 'Ilutt cut." 

Position in treo (with relerencc to periphery) Not known. 

aiae of te.st material ; I 

I.cn-th 4 



Breadth . 

I)e]>th imeasurt'd acrosH rings). 

NuniluT of rings 

Width of ringrt (average) 

SumnuT wood as a whole 

Finn hast tissnc 

Space lost hy lariio ve.-<nel8 

Moisture conditions when tcsled... 
Density 



\% inch. 
\% inch. 

*J.7 inillinietcrs. 
80 per cent. 
(10 j)er cent. 
14.7 percent. 
Nearly seasoned. 
.81 



A. b. II. Connec- 
ticut lowland. 

Southwest. 
" Butt cut." 

Not known. 


B. Arkansas. 




4 

Ig inch. 

\l iueh. 


^Noi specilied. 


1.5 uiillimeters. 
7)4 per cent. 
:i7.5 per cent. 
24.9 percent. 
Half seasoned. 
.77 





These particular tests can hardly settle defiuitely auy question. Samples 1 and 13 being 
selected stock, second growth, can not be used for comparison with samples of B, except to show 
that for stillness the unselected Southern stock is superior to the best Northern growth, as also iu 
resistance to endwise compression. The samples 3, 4, 5, and 6 are probably more nearly compara- 
ble to samples of B, and here we lind the Southern oak very much superior, not only in stitfuess 
and (H)lumnar strength, but also iu ultimate crossbreaking strength, while for resistance to shock, 
at least one sample of Southern oak is superior to three samples of forest-grown Northern, and 
even to one of the best Northern second growth. This piece (No. 8) exhibits, altogether, qualities 
which render the verdict tenable that Southern oak is not necessarily inferior to Northern oak in 
any of its qualities. 

Beyond this it would not be safe to use these ligures for generalizations. 

In 18S.S the really first beginning in timber physics was made in the form of a preliminary 
physical and structural examination of a set of trees representing the more imijortant lumber ijines 
of the South and of the lake region, as well as of bald cypress. A comprehensive plan was fully 
worked out and the mistakes of former methods were carefully avoided. In 1891 a more extensive 
study of the four great Southern timber pines, the longleaf, Cuban, loblolly, and shortleaf, was 
begun, and the material was at the same time collected in such a manner as to enable a detailed 
inquiry into the relative merits of timber bled or tapped for turpentine as compared with unbled 
timber. 

The trees were collected by ]>r. Charles Mohr, of Mobile, Ala., an acknowledged authority on 
the botany of the region, and thus a correct identification was assured. Of each tree entire cross 
sections as well as the intervening logs were utilized, the former being subjected to examinations 
into their specific weight (the acknowledged indicator of many valuable technical properties), iuto 
the amount of moisture contained, into the shrinkage conse(iueiit on drying, and into the struc- 
tural peculiarities, particularly those structural features which are readily visible and may be 
utilized in practice for purposes of timber inspection. 

The logs were sawed and tested according to definite plans in the well-equii)ped test laboratory 
of the Washington University, St. Louis, Mo., under the direction of Prof J. B. Johnson, a recog- 
nized authority in engiueering. The first series of test results are embodied iu BuUetin No. 8 of 
the division, where the strength values for the longleaf pine are fully tabulated and discussed. So 
eagerly was this bulletin sought by Avood consumers, that an edition of J,000 copies was exhausted 

in a Short time. 

Bled and Unbled I'ine. 

In addition, this series of tests together with an extensive chemical analysis aud physical and 
structural examination of material from unbled and bled trees, as well as from trees bled and 
abandoned for five years, re-enforced by an extended study of bled and unbled timber at various 
points of manufacture, proved conclusively that the discrimination against bled timber was 
unwarranted, since the bled timber was neither distinct in appearance, behavior, nor strength. 

To avoid error in so important a matter, and also for a comparison of the three most important 
turpentine trees — the Cuban aud longleaf with the loblolly pine — the extensi\ e chemical analyses 
of Dr. M. Gomberg, of the Michigan University, were repeated and extended by Mr. O. Carr, of 
the Chemical Division of the Department of Agriculture. This series of additiomil chemical 



RESINOUS CONtKNTS OF PINE. 333 

analyses fully substantiated Dr. Gomberg's work, so that it was safe to announce that: (1) Bled 
timber is as strong as un bled timber; and (2) that it contains the resinous .substances in the same 
■miounts and similarly distributed as the wood of unbled timber, so that it seemed to follow as a 
simple corollary that bled timber is also as durable as unbled, and hence e.iual to the latter in 

every respect. . . , . ^ , , i ^i 

The importance of this fact was quite fully realized. Trautwine, in his standard work, the 
Engineers' Pocketbook, at once placed the fact cm eminent record, and the lumbermen ot the 
South, as well as all trades Journals, spread the welcome news in every paper and at every 

opportunity. . ,, . ^, , ,, ,.,,. , 

The work of Mr. (lombcrg in determining the distribution ot the resin through the diflerei.t 
parts of the tree is uni-iue in method and classical in its clear scientific procedure and statement. 
Since the publication in which it first appeared was at once exhausted, it appears proper to repro- 
duce it in full, leaving out only a few tables, as a part of the most valuable work m timber physics 
performed under direction of the Division of Forestry: 
A Chemical Study op the Resinous Contents and their Distribution in Trees of 

THE LONGLEAF PiNE BEFORE AND AFTER TAPPING FOR TURPENTINE. 

[By M. (ioMUKRO.] 

Botanists tell us that resins are produced by the disorganization of cell walls and by the 
breaking down of starch granules of cells. Chemists believe that resins are oxidation products of 
volatile oils, the change being expressed by formula as follows: 2C|„H„;+30=C.,„H,„O,+H,O. 

Whatever view be correct,' one thing is certain, and that is that the formation ol either resins 
or essential oils requires the presence in the tree of those peculiar conditions which we call vital. 
The tree must live, must be active, must assimilate carbon dioxide and imbibe moisture, in order 
that oil of turpentine and rosin be formed. 

The heart of the tree is the dead part of it. It does not manufacture any turpentine. A part 
of the oleoresin in it had been formed when the heartwood was yet sapwood, and remained there 
after the change from sap to heart had taken place. It is also probable that the heart of the tree 
acts as a .storehouse in which there is deposited a portion of the oleoresin formed m the leaves 

and sap. • i ^ i i 

When a tree is tapped for turpentine there are two possible changes that might be supposed 
to take place: (1) The tree may be considered as jdaced in a, pathological condition, when it will 
strive to produce a larger amount of oleoresin in order to supply the amount removed. In a few 
years the ener^ry of the tree will be exhausted and the amount freshly supplied will fall far below 
the amount of oleoresin drawn oft by the tapping. The tapping will then have to be discontinued. 
The oleoresin in the heartwood will in this case remain untouched. (2) The oleoresin previously 
stored away in the heart might, by some unknown means and ways, also be directed toward the 

wound. 1 • 1 

If the first change takes place then, the tapping will have little effect upon the chemical 
composition of the heartwood. If, however, the second condition prevails during tapping, then 
of course the heartwood will be seriously atfected for some time afXer tapping, and will contain a 
much smaller amount of oleoresin than it contained before tapping. Moreover, the tapping may 
affect not only the amount of oleoresin, hut also the (luality of the new product and the relative 
distribution of volatile products. „ , , * 

For this reason the chemical side of the problem has been approached by parallel analyses ot 
tapped or untapped trees for their relative amounts of turpentine. It was hoped that by a large 
series of analyses an average might be obtained showing whether tapped and untapped trees difter 
from each other in that respect. 

CHEMICAL COMPOSITION OF TURPENTINE. 

Under the name of turpentine is known an oleoresinous juice produced by all the coniferous 
trees in greater or less amount. It is found in the wood, bark, leaves, and other parts of the 
trees. It flows freely as a thick juice from the iiujisions in the bark. It con.sists of resm or resins 

' The one view does not e.'ccliide tlie utker. 



334 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 

dissolved iu an essential oil; the latter is sejiarated from the former usually by distillation -with 
steam. 

There are many varieties ot turi)entine, corre-siioiidinj^ to the different varieties of coniferai, 
but only three are commercially important, as tliey are the source of the three principal oils of 
turpentine. 

(1) Tiie turpentine of PinuK pinmtvr (syn. P. maritima), collected in the southern departments 
of France around Bordeaux. From it is obtained the French turpentine, which yields 25 per cent 
of volatile oil. 

(U) The turpentine from rinus palmtris^ P. twda, P. luterophyUa, collected in the southern 
sea-borderinf>' States from North Carolina to Texas. From them, principally from the first source, 
is obtained the English or American oil of turi)entine, which yields 17 per cent of volatile oil. 
Formerly the 7*. ri<ii(hi was also worked for turi)entiiie in the North Atlantic- States, but it is now 
exhausted. 

(.'5) The turpentini! from I'inih laricio var. aiiMriaca, collected mainly iu Austria and Galicia. 
From it is obtained the (ierman turpentine oil, which yields 32 per cent of volatile oil. 

The IJussian oil of turpentine is obtained from Plniia xiircstrisi and riniif; Icdebourii, hy the 
direct distillation of the resinous wood, without previously collecting the turpentine. It is said to 
be identical with the German oil of turpentine, but more variable, as it contains products of 
destnicfive distillation, both of wood and rosin. 

The turpentines from tiie dirt'erent sources differ from each other — (1) in their action upon 
polarized light, (2) in the relative amounts of volatile oil they yield on distillation witli steam, and 
(.'?) in the nature of the volatile oils they contain. 

(Utloplioiuj. — The rosin in the different varieties of turpentine is practically the same. It is 
known as common rosin or colophony.' It consists chemically of a mixture of several resin acids 
and their corres])onding anhydrides. The chief constituent is abietic anhydride, CjjIIiaO^, abietic 
acid being GjjUi.jO.,. Tlie crystals that are noticed in crude turpentine are the free abietic acid; 
on melting the thick turpentine, or on distilling the volatile oil, the acid is changed to the anhy- 
diide. Colophony is nonvolatile, tasteless, brittle, has a smooth shining fracture, sp. gr. about 
1.08. It softens at 80° 0., and in boiling water melts completely at 135° C. 

The rohitilc oil. — The second ]iriucii)al constituent of turpentines are the volatile oils. The 
chief ingredient of the three turpentine oils is a hydrocarbon of the same composition, C|„H,u; 
nevertheless the three oils have distinct hydrocarbons differing from each other in physical if not 
in chemical properties. The empirical formula of the hydrocarbon is CioHn;, and according to the 
latest researches of Wallach- it has the following structural formula: 



cm 

CM 




thus being a dihydropara-cymene, i)aracymene being CioHu, 

CJffCJ/jJs 
C 

ffcr ^c/f 



EX 



CCHa 



OB 



' Colophon, a city of Iconia, whence rosiu was obtained by the Greeks. 
■Ann. Chem. (Liebig), L'Sit, 49; Ber. d. C'heni. Ges., 21, 1515. 



RESINOUS CONTENTS OF PINE. 335 

The position of this particular terpeue, piiiene, will be best seeu from the general classifica- 
tion of terpenes taken from Wallacli.' 

I. Memiterpemx or pcnteiics of the formula CjHs. 

II. Terpema or dqxnienex of the foriimhi ChJIm;. 

(1) I'inene, ohtniuoil fioiii many varietii'S of turpentine. 

(2) Camphoie, obtained artiiicially from camphor. 

(3) Fincheiic, obtaineil artificially from fenebone, a constituent of many fennel oils. 

(4) Lcmoneiiv occurs in orange-peel oil, in oils of lemon, bergamot, cumiriiu, etc. 

(5) Dipeiiienc, obtained artificially from piuene. Occurs m Russian and Swedish turpentine. 

(6) St/lrestrcne occurs in Russian and Swedish turpentine. 

(7) Phelandrene occurs in the oils of bitter fennel and water fennel, elcnii, eucalyptus. 

(8) Tapinenc occurs in oil of cardamom. 

(9) Topinolcne, only slightly known. 

III. — roliiterpcnes, of the formula (CsHs),,, as c<;droncs dsHj, caoutchouc (CsHs),,, etc. 

The hydrocarbon of the American and French oils of turpentine is pinene. It is dextro- 
rotatory when obtained from the American turpentine oil, and is known as austro-terebinthene 
or australene; hevo-rotatory when obtained from the French tnrjjentine oil, and is known as 
terebintheiie. Otherwise the two hydrocarbons agree entirely in specific gravity, boiling point, 
and behavior toward chemical reagents. 

The hydrocarbon of the Eussiau oil of turpentine is sylvestreue. It is dextro-rotatory, and 
has a higher boiling point than pinene. The latter boils at 155° to 150° C, the former at 175° to 
178° G. 

But even the turpentine oils af high grade as found on the market do not consist of pure 
pinene; e.siiecially is this true of ordinary oil of turpentine, which is obtained from the cruder 
turi)entine by a single distillation with steam. Ditferent samples vary from one another 
considerably in their si)ecific rotatory jwwer as well as their boiling point. 

Ameri(-an oil of turpentine has a density of O.SOdo to 0.870°. According to Allen- it begins 
to boil at a temperature between 150° and 100° 0., and fully passes over below 170° 0. "A good 
sample of rectified American oil will give 90 to 93 per cent of distillate below 105°, the greater 
jiart of which will pass over between 158° and 100°''," while in the experience of J. H. Long,^ 
"In the examination of a large number of pure commercial samples of turpentine oil it was 
observed that the boiling point was uniformly at 155° to 156°, and that 85 per cent of the samples 
distilled between 155° and 163°. The distillation is practically complete below 185° O." 

Then, again, as found by Long, the vapor densities of many samples of oil are too high to 
allow the fornnda CioH,,; for the entire oil. Fractions of different boiling points show diflerent 
degrees of specific rotation. All this would indicate that ordinary turpentine oil contains 
hydrocarbons heavier than pure pinene, OiuH,,;. They are probably either isomeric with pinene, 
but of a higher boiling point, or may belong to the polyterpenes. 

Still less do we know of tiie source of these hydrocarbons. Whether they are produced by 
the tree simultaneously with i)inene, and are therefore to be found in the oleoresin or whether 
they are all or in part produced by external agencies after the turpentine has been dipped c^an not 
be answered. Probably the formation of these other hydrocarbons takes place in both ways 
spontaneously in the tree and by some influences outside the tree. 

Indeed, all terpenes have this property in common that they easily undergo change, from 
optically active to inactive, from hemiterpenes to terpenes and polyterpenes. The change can be 
brought about either by heat alone, or by heating the terpenes with salts or acids. So, when a 
sample of American turpentine oil of +18.0° was heated to 200° 0. for two hours it showed an 
opposite rotation of — 9.9°."' Pinene heated to 250° to 300° C. is converted into dipentene GH, 
boiling at 175°, and a hydrocarbon CH, boiling at 200° C. 

These illustrations will suffice to show that the transformation of iiinene into isomeric and 
heavier hydrocarbons may occur, at least partially, after the turpentine has been removed from 
the tree. 

' Ann. Chem. (Liebig), 227, 300; Ber. d. Chem. Ges., 24, 1527. ^ Allen, Com. Org. Anal., 2, 441. 

s Allen, Com. Org. Anal., 2, 437. ■'.Tour. Anal, and Appl. Chem., 6, 5. 

'Muspr.att's Chemio, 4th ed., 1, 153. 



33() FORESTRY INVESTIGATIONS U. S. DEPARTMENT OP AGRICULTURE. 

The crude turpeiitiiu! from I'iniis palustris, or long-leaf pine, is thus made np of — 

(1 ) Kosiii, 75 to 90 j)er cent ; mostly abietic auliydride. 

(2) Australene, 2'< to 10 per cent: boils at 15r> to 156° C. 

(.'!) Some other tcrpeiies of Cii.Hinj snjall portions ; kind uot known. 

(4) Some polyterpenes of (Cfilla),,; small portion.s; kind not known. 

(5) Cymene (?) C,,,!!,,; small portion.s, if any; boils at 175^ to 176° C. 

(fi) Tracrs of formic and acetic acids; produci'd probnbly Tiy atmosjdieric oxidation dnrin<; collection of 
tnrpontine. 

ANALYTICAL WOKK. 

As both till' lo.sjn and the vohvtileoil are easily soluble in chloroform, ether, carbon disnlphide, 
etc., their separation from wood by any of the above solvents would appear to l)e an easy matter. 
But an exact (|nantitative determination of the volatile oil presents considerable diliiieulties, and 
for these reasons: (1) ^Vood (-an not be dried free from moisture without driving off some of the 
volatile hydrocarbons; (2) the ether extract can not be freed entirely from either without some loss 
of the volatile oil. 

If a weighed (juantity of wood shavings is exhausted with either, the i-esidue dried at lOQo 0. 
and weighed, the total loss thus found will represent: 

The moisture = H. 

The rosin = R. 

The volatile hydrocarbons = T. 

It is sntticieiit to deteimine two of these factors; the third could then be determined by 
difference, lint as has been mentioned before, the ether extract can not be obtained in any degree 




^SJ 



I-'h;. 85. — Metlioil lit clicmic;!] :iTi;iIysiH nf tii["l>fiitiiii-. 

of purity without loss of turpentine. The evaporation of ether in a stream of dry air, as proposed 
by Dragendoif, fiir the estimation of essential oils in general, does not give satisfactory results 
with turpentine oil, as Dragendorf himself observed. 

A weighed quantity of a mixture of rosin and oil, made up in about the same proportions as 
they exist in crude turjientiiio, was dissolved in a suitable amount of ether. The latter was then 
evaporated in a current of dry air till the odor of ether was hardly noticeable. The mixture was 
found to have gained considerably in weight by retaining ether in the thick sirupy oleorosin. It 
was only by heating at 100° C. for some time that all of the solvent could be driven off, and then 
the mixture was found to have lost in weight. Repeated trials proved that this method could not 
be used safely. 

An attempt was then made to determine the quantities fi'and R, and thus find T by difference 
A weighed quantity of wood shavings was placed in a small tlask a. The latter was connected 
on one side with a tray of drying bottles, on the other two OaCl, tubes h and c, similar in size 
and form. The tiask is immersed in boiling water and a current of dry air is passed through the 
whole apparatus for one and one-half Ijours. The flask is then cooled and air is i>assed for one 
and one half hours longei'. 

It was thought that while b would retain all the moisture and a i)ortion of the volatile com- 
l)ounds,c would retain about the same amount of the volatile products only. Gain in weight of 



INVESTIGATIONS INTO RESINS. 



837 



c subtracted from that of b would then give the moisture H. The sample of wood shavings is 
then exhausted with ether, the latter evaporated, and the residue heated at about 140'^ to 150° to 
constant weight; this gives the rosin B. If L be the total loss by extraction with ether, we have 

L-H+R=T. 

But it was soon found by experiments upon pure turpentine oil that the two CaClj tubes did 
not retain an equal amount of volatile oil. The quantity retained depended upon many circum- 
stances, the chief one being the amount of moisture already present in the CaCL tubes. 

Even had the tubes retained (pxantities of turi)entiiie oil, this method would still have the 
objection that one of the constituents was to be determined by ditterence — an objection especially 
serious when the ingredient to be so determined is small iu comparison with the materials to be 
weighed. 

The writer has therefore attempted to make use of a somewhat diflerent principle. A few 
trials were sufficient to show that the method promised to give satisfactory results. The basis of 
the method is the same which served for the production of Eussian turpentine oil on a large scale, 
namely, the distillation of the volatile products from the wood itself, without previously obtaining 
the turpentine. But instead of condensing the volatile products, their vapors are passed over 
heated copper oxide, whereby they are burned to water and carbon dioxide. Many trials were 
made with this iT.ethod upon pure materials and ou samples of resinous wood. As the results 
were found to be entirely concordant and satisfactory, the method was adopted, and by it were 
obtained the results presented in this report. 



DESCRIPTION OF THE METHOD EMPLOYED. 



A weighed amount of wood shavings is placed iu a straight CaOL tube «. The tube is con- 
nected on one side by means of a capillary tube with a drier A, which serves for freeing the air 
from moisture and CO,,. The other end of the tube is connected with an ordinary combustion 




Method of distiUutiou of turpeutiue. 



tube h containing granulated CuO. Tiie tube is drawn out at one end as is shown in the figure, 
and the narrow portion is loosely filled with asbestus wool. The connection is made glass to 
glass, so that the vapors of distillation do not come in contact with any rubber tubing. The 
forward end of tlie combustion tube is connected with a CaUl^ tube c, one-half of which is filled 
with granulated CaCli and the second half with 1^0,,. Then follows a potash bulb d provided 
with two straight tubes, the first one filled with solid KOH, the second with P.O,-,. The last tube 
is connected with an aspirator. 

All the connections having been made air-tight, the connection between the tube a and the 
drier A is shut off by means of a clamp and the aspirator turned on. When the combustion tube 
has been heated to dull redness the burner under the air-bath B is lit and the temperature raised 
to IIO'^-IL'O^ C. The moisture contained in the tube escapes quite rapidly, carrying with it some 
turpentine oil. The capillary tube at the other end of A practically checks backward diffusion 
H. Doc. 181 22 



338 



FOKKSTUY INVESTIGA'I'IONS U. S. DEPARTMENT OF AGRICULTUIiE. 



or any accuinulation of condensed vapors. In about fifteen minutes all the nioistui'C appears at 
tbc forward end of the coMibastion tube. Tlio clamp is now opened and a stream of air at the 
rate of somewhat over one liter an hour is passed through the whole ai)paratus, while the tem- 
perature of the air bath is raised to 15.">^ to IGO'^ C, and kept at that point for about forty-tive 
minutes. Toward the end of the oi)eration the temperature is raised to Kio'^ to 170° C. for teu 
minutes. Then the light under the air bath is turned off and air aspirated for twenty to twenty- 
live minutes longer. As the air bath is in close contact with the combustion furnace, the whole 
length of the tube is kept at a temperature above the boiling point of turpentine oil. In this 
way a coiiiijlete distillation is insured. 

All the moisture is retained by c, while the CO^ is absorbed in the potash bulb d. The gain of 
weight in c represents the moisture originally present in the sample of wood plus the water 
produced in the combustion of the hydrocarbons. The gain in weight of d represents the amount 
of CO2, derived from the combustion of the volatile products. 

The tube a is now transferred to an ordinary Soxhlet's extraction apparatus and exhausted 
■with ether. The latter is distilled otf, the residue dried for about two hours at lOO^ C, and 
weighed. This represents the amount of rosin in the sample of wood taken. 

As has been previously mentioneil, the volatile oil of the oleoresin is not pure australene, 
Oii,Hii; = (CsH,.)... It j)robably contains some other hydrocarbons, either of the same formula or 
belonging to the class of polyterpcnes (C5H,,),,. It is clear that whichever they be their percentage 
comjiosition is alike in all; they all have C= 88.23 per cent, H = 11.77 per cent. Therefore, so 
far as the combustion of the volatile terpenes is concerned, they can all be represented by the 
ecpiatiou: 

(J„,H„, + 140 = 10 00.,= S H.O 



130 



440 



144 



In other words, 440 parts of COj are derived from 136 parts of volatile terpenes. 

440 rlSO = 1 : X ; X = 0.3091 , 
i. e., 1 partof CO.. ol)taiii('(l in the combustion represents 0.301) parts of (he volatile hydrocarbons. 
For every 410 parts of OO3 produced there are 144 parts of H3O formed. 

440 :144 = 1 :X ; X = 0.3272, 
i. o., simultaneously with 1 i)art of CO2 there is produced 0.327 ijarts of HaO. 
Let the weight of the sample taken = W, 
Let the weight of CO^ obtained = W, 
Let the weight of HjO obtained = W", 
Then — W x 0.309 = T, the amount of volatile hydrocarbons. 

W X 0.327 = II', the amount of II^O corresponding to the volatile hydrocarbons. 
W" X — H', = n the amount of moisture in the wood. 

T II 

^ = per cent of T; «t= per cent ot moisture. 

Thus the moisture, the volatile hydrocarbons, and rosin are obtained directly from the same 
saimi)le. Where many estimations are to be made, it is of course unnecessary to cool down the 
combustion tube between successiv'e combustions. 

The temperature of dutiUatwn. — Some experiments were made to determine at what tempera- 
ture it is safe to conduct the distillation. Although pure turpentine boils at 15G-lG()o C, yet in 
open air it (-an be volatilized at a nuich lower temperature, even on the water bath, without any 
difficulty. Especially is this the case when the vapors are removed as soon as formeil by a stream 
of air, but it must be remembered that the volatilization of the essential oil directly from the 
wood might be considerably hindered by the large amount of rosin. 

A sample of wood distilled by the method outlined above gave the following results at 
difierent temperatures: 





120° 


140° 


1501^ 


160° 


170O 


H,0 — 


l*er cent. 

1.09 

11,17 


Per cent. 

1.18 

11.33 


7'er cent. 
1.3U 
11.23 


Per cent. 
1.20 


Per ce7it. 
1.32 1 











INVESTIGATIONS INTO RESINS. 



339 



Another sample gave : 





160° 


180" 

1 


HjO = 


Per cent. 
4. no 

8.79 


Per cent. 
3.98 





The results would indicate that the distillation is practically complete at 160°, and that iJie 
wood itself does not contribute any CO, by partial decomposio!i at that high temperature; for, 
should the latter be the case, higher results might bo expected at ISO'^ than at IGOo, and then the 
sapwood would give much higher numbers for turpentine oil than those actually obtained. 

Even if this method does not give the absolute amounts of volatile hydrocarbons, yet it 
certainly gives results very near the truth, and, what is more important, under the same conditions 
it gives constant results. Therefore, by employing strictly parallel conditions in the analysis of 
the different samples, results are obtained which can be safely used as indices of comparison 
of the relative amounts of volatile hydrocarbons in the samples under analysis, 

MATEKUL FOU ANALYSIS AND METHOD OF DESIGNATION. 

Material)). — Trees No. 52 and 53, abandoned five years. 

Trers No. 60 and 61, abandoned one year. 

Trees No. 1 and 2, not tapped. 

Trees 54-57, abandoned five year.s. 

Trees 58-59, abandoned five years. 

Trees 63-65, abandoned one year. 

Trees 66-69, abandoned one year. 

Trees 17-19, not tapped. 
Generally Disk 11 is 23 feet from ground. 
Disk 111 is 33 feet from ground. 
Disk IV is 43 fret from ground. 

Method of designation. — It was thought best to make a somewhat detailed analysis of a few 
bled and unbled trees in order to gain an insight into the quantitative distribution of turpentine 
in the trees. Each disk was divided into pieces of about thirty rings each, the heart and sapwood 
being kept separate. The number of the disk is designated by a roman iigure, the kind of wood 
by either .i for sapwood or h for heartwood. The arabic figure which precedes the h or s de.siguates 
the number of the piece, counting for the sapwood 
from the bark; for the heartwood, from the line of 
division between sap and heart. 

PreiHiration of material. — The first six tables 
give the results of what might be called "detail" 
analysis, where each piece of about thirty rings has 
been analyzed separately. The material for analy- 
sis was prepared in the following way: A radial 
section of the disk, about 1 to 2 inches thick, is 
selected. A piece of 1 inch is cut off transversely, 
and the strip is then divided into pieces of about 

thirty rings each. From the freshly cut transverse surface about 15 grams of thin shavings are 
planed off and placed in a stoppered bottle. The exact amount used for analysis, usually from 3 
to 5 grams, is found by weighing the bottle before and after taking out the portion for analysis. 

The second set of tables, VII to XII, inclusive, give the results of "average" analysis. The 
material for these analyses was obtained by mixing equal quantities of shavings from the corre- 
sponding portions of several trees and taking for analysis an average samjjle of tbe mixture. The 
sapwood furnish one analysis and the heart wood was either analyzed as a whole or divided into 
portions, 1/t and 2/t, if of considerable thickness. 

Notes on Tables I to XII. 
Each table contains a column "calculated for wood free from moisture," giving the per tent of volatile hydro- 
carbons and rosin obtained by calculation from results actually found. Objections might be raised to this mode flf 
interjireting the results. It might bo said that the moisture in the wood can not be disregarded, because it is as 
much an essential proximate constituent of wood as the turi>entine itself is. But since the analyses were not made 
soon after the trees had been felled, the moisture found in the samples does not represent the original moisture, nor 



Is 



2a 



IK 



3K 



47i. 



Fk;. 87. — Distribution of turpeutino iu trees. (A piece marked 
52 HI 2/i moaus tree No. 52, disk III, tlio second piece of the 
heart t 



340 



FORESTRY INVESTIGATIONS TJ. S. DEPARTMENT OF AGRICULTURE. 




-Itelationsbiji of dillerent jtarts (iT sairni 
(IJak. 



does it represent eqii.il portions of it in all samplfs. 'I'lir nuniltcrs given in tlie column ''water" are of course 
suggestive as to the comparative degree of retention of moisture Ijy the diflercut samples, since the latter were all 
exposed to about the same inlluenccs. But it seemed best to compare the amounts of volatile hydrocarbons and 
rosin on wood free from that variable constituent; the more so as sometime elapsed between the analysis of the 
lirst and last samples. 

The last column in eacli table contains the ratio lietweeu the volatile hydrocarl)ons and rosin. Tliis ratio is 
multiplied by 1(10, and moans that for cnery 100 parts id' rosin as many parts of the volatile hydrocarbons are found 

as is Indicated in the column. 'I'liis ratio [ \ is of little value in cases when th(5 amount of turpentine is small, 

because a very small increase of (he lirst constitnent — an increase within experimental error — will change the 
quotient considerably. An increase of 0.07 per cent of volatile hydroi'arbons in 60. IV, Is will bring up 

- from 7.2 to 10. ,\ decrease of 0.07 jier cent in 52, IV, 2» will change - from 2.'). 20 to about Ul. These numbers 

arc therefore of very little sij;ni1icance when applied to the sapwood of all sanii)les, to entire tree 52, and to some 
parts of trees (iO and 1, all of which show only small ijortions of turpentine. 

DISCUSSION OF RESULTS OBTAINED. 

Kelation of rosin and rolntilc hydrocarbon to moisture. — -The iiinount of moisture retiiiued by 
ditt'erent samples does not seem to have any direct relation to the amount of oleoresin in these 
samiiles. Yet in the same tree, or rather in the dift'erent parts of the same disk, there seems to exist 

something like a relation of the two. This is especially notice- 
able in tree JSTo. 53. The moisture retained seems to vary in- 
versely with the amount of oleoresin in the sample. Compare, 
for example, in "».'> II, Ih, 2h, 3li; in 53 III, l/(, '2h, 'Mi, 4/t; in 
53 IV, 2A, 3h, ih. The piece richest in oleoresin is generally 
the poorest in moisture. But this is by no incan-s a universal 
rule. Some trees show about the same per cent of moisture 
in parts widely <lifferiiig from eacli otlier in the amounts of 
turpentine, and in many instances a smaller amount of tur- 
pentine is associated with a smaller per cent of moisture. 
iSapirood and hrartirood. — All the analyses, detail and average, show conclusively that the 
sapwood is comparatively very poor in turpentine; it is immaterial wliethcr it co:i;es iiom a. ricii 
tree or a poor one, from a tapped tree or an untapped one. The turpentine in sapwood reiicli(\s 
3 to 4: per cent in very rich trees, as in Nos. 53, Gl, and 2; in the remaining trees it is li to 3 iier 
cent. Conse(iuenlly the results obtained for sapwood are not taken into account in the following 
paragraphs. When differences between trees are spoken of, it applies entirelj^ to heartwood. 

The ditt'erent i^arts of the same disk show a constant relation in nearly all instances. In 
most cases 1/; is the richest, and the heartwood grows poorer as we approach the pith of tiie tree. 
In a few cases, as in 1 III ami in 1 IV, l/i and 2/t are iiractically identical, while in some instances, 
in li III, (Jl 11, 01 III, and 53 II, Ih is poorer than 2h. In nearly all cases the decline is marked 
in 37i, and 4/t is usually found to be the poorest part of the disk. This relationship can be 
represented in a general way by the following curve: 
liclation of volatile hydrocarltoiix to rosin. — As the 
turpentine in the tree is a solution of rosin in an essen- 
tial oil, it will follow that the richer a tree is in tur- 
pentine the richer it will be in the constituents that go 
to make up this mixture. One would also expect that 
the ratio between the volatile hydrocarbons and i-osin 
would be tolerably constant in the diflerent parts of 
the same tree, but the results of analysis do not indi- 
cate it. They show that this ratio increases with the 
amount of rosin. A part of heartwood having twice as nuich rosin as another part will contain 
more than twice as much volatile jiroducts as the second part. This is true in a general sense 
of parts of the same disk, of parts of ditt'erent disks in the same tree, and parts from ditt'erent 
trees. There is no distinction in that respect between bled and itnbled trees. This relationship 
can be formulated in the following way: The crude turpentine from lieartwood rit^h in oleoresin 
will yield a comparatively larger amount of turpentine oil than the turpentine from heartwood 
poor in oleoresin. 



Ill 


3},, 


3h 


4h. 



¥ui. 89.- 



-Yield of volatile oil liuiii 
til rpen tint'. 



coiistaiit iiuaiitity of 



INVESTIGATIONS INTO RESINS. 



341 



It has been shown that the heartwood grows poorer from l/( toward the pith of the tree. It 

T 
will therefore follow from what has been said in the preceding paragraph that -^ will also grow 

smaller from Ih to the pith. The yield of volatile oil from a constant (piantity of turpentine 
can be expressed in a general way by a graphic illustration similar to that which expresses the 
yield of total oleoresin from different parts of the disk. 

T 
It is difficult to explain satisfactorily this decrease of jj- The two parts of the radial sec- 
tions that have been the longest exposed to air are l.v and the last h. The question naturally 

T 
arises, May not the decrease of ,, be due to a greater evaporation of volatile hydrocarbons from 

these two euds ? But this can hardly be so. No. 53, IT, 47i was analyzed at intervals of two 
months and furnished the following data: 



I, Sept. 28. 


II, Nov. 27. 


Hj0=11.23 
T =1.30 
14 = 7.90 


7.24 

l.a4 

8.12 



Calculated for wood free from moisture: 



I. 

1 


11. 


i 

1 T=1.30 
K=8.9(i 


1..10 
B.75 



Sufficient experimental data are lacking to prove conclusively that the volatile hydrocarbons 
do not evaporate to any extent from tlie heartwood except from freshly cut surfaces of it. 

Relation heiween different (?/.s7,.s of the same tree.— There is no constant relation between the 
different disks of the same tree so far as the amount of oleoresin is concerned. Although the 
disks do vary from each other, the variation can not be connected with gravitation, by virtue of 
which the lower disks would contain a larger amount of turpentine than the upper ones; for dif- 
ferent trees vary from each other considerably in this respect, the variation being apparent in 
both bled and unbled trees. If a, h, c stand for the amounts of oleoresin in disks denoted by 
Roman numerals, the relative magnitudes being represented by the letters in the alphabetic order, 
then the results of analysis can be condensed in the following table for the trees denoted in Arabic 
numbers: 





53. 


60. 


CI. 


1. 


2. 


IV 

III.... 
II 


a 
b 


h 
c 
a 




a 
b 




c 
b 


c 
b 
a 



It is evident that no constant relation as to amounts of oleoresin exists between the disks of 
the same tree. 

Comjxirison of tree 5:? with 53. — These two trees were both supposed to have been sound, 
healthy trees at the time of felling, and yet they differ from each other as much as two trees could 
differ. The heartwood of one is very rich in turiientine; that of the other contains comparatively 
very small quantities— only a trace. How to explain the difference! Previous to felling they had 
both been tapped for four consecutive years; consequently both must have contained considerable 
amounts of turpentine. Since the last tapping they stood for five years side by side, both exposed 
to the same inlluences. This great difference can not be traced directly to tapping, for the latter, 
itmay be assumed, would have aflected both treesequally. The cause of the difference between 53 and 
52 ought to be looked (or, rather, in the condition of the two trees before tapping. In connection 
with this it would be interesting to know how much turpentine each tree had yielded when tapped. 

Comparison of trees 00 and 61. — There is a decided difference between the two trees. The high- 
est numbers in 60 are 0.84 per cent for volatile hydrocarbons and 5.35 for rosin, while in (>l 0.75 



342 



FORESTRY INVESTIGATIONS IT. 



DEPARTMENT OF AGRICUT.TURE. 



and 5.67 are the lowest numbers for tlie corresponding constituents, the highest being 3.40 and 
l(i.2!l, resitectively. Here aguin we have two trees of about the same age, under apparently the 
same conditions of growth, t;ip])('(l at the .'^ame time and abandoned for the same length of time 
before felling, and yet dilfering very widely from each other. It is dihicult to conceive why tap- 
ping shimld have affected the heartwood of these two trees in such a strikingly different manner. 
If the assum])tion is made that the tapping had drained l)oth trees equally, what explanation can 
be gi v(Mi Ibr the fact that within one year of abandonment one tree is very rich in turpentine while 
the other has less than one-fourth as much? 

Vomparixon of trees ~)S uiid 53 iriih CO and 61. — Compare 53 and Gl. Here we have two trees 
both very rich in tnrpentine, but while 53 had five years of rest after tapping, (il had only one 
yeai'. Had the tapping forced the trees to pour out their oleoresin previously stored up in the 
heart, we should ex]>ect to find in the time of rest the prime factor lor the tree in resuming its 
natural condition ; but, on the contrary, results of ainilysis show that time of abandonment before 
felling is of little importance. While we can have a tree very rich in turpentine within five 
years after tapping, we can also have trees rich and poor even within one year, and trees almost 
totally deprived of turpentine in the heartwood within five years after tapping. 

Comparison of 1 with i'. — These two trees had never been tapped, and yet neither is rich in 
tnrpentine. No. 2 contains about twice as much turpentine as No. 1, the difference becoming 
smaller as we go up the tree. The highest numbers for 2 are 1.93 and 14.19 for T and E, respec- 
tively, the lowest 0.8C and 5.89, with an average of about 1 and 7. We can say that there is as 
much dift'erence between untapped trees as there is between trees that have been tapped. 

Average analyses. — The average analyses cover IC trees. Thirteen trees furnish four sets of 
analyses of tapped trees and 3 treses fnrnish one set of untapped. The results obtained are 
summarized in the following table: 



Tree No. 


II. 


III. 


liem.arks. 


T. 


B. 


J^-XIOO. 


T. 


Jt. 


I'xioo. 


54-57 
57-. 19 
63-65 
66-69 
17-19 


Per cent. 
0.93 
.80 
.91 
.89 
.64 


Per cent. 
5.88 

4. "6 

5. .32 
4.95 
2.98 


15. 58 
19.63 
17.18 

18 
21.37 


Per cent. 

U.5S 

.82 


I'er cent. 
3.98 
4.29 


14.04 
19.10 


Abandoned 5 veans. 

0... 
Al>andoned 1 year. 

D.i. 
Not tapped. 


.71 


3.21 


21.76 



These results show a pretty constant average number for turpentine in tapped trees. The 
heartwood of untapped trees is poorer in both volatile oil and rosin than that of tapped trees. 
And here again it is worthy of notice that time of abandonment is of little importance to tapped 
trees. The trees that had been abandoned for one year are fully as rich as those that had five 
years to recover from tapping. 

Comparison <f tapped a'ith untapped trees. — If now the heartwood of tapped trees be compared 
with that of untapped, one is at a loss as to what conclusions should be drawn from so few 
analytical data. It is remarkable that the two richest trees and the poorest tree are among those 
that had been tapped. Of the remaining 19 trees, there is no difference between the 14 tapped 
and 5 unta])ped. Whatever differences are found among liled trees are equally found among 
those that have not been tai)ped. 

Indeed, from the study of the results of analy.ses the writer is of the oijinioii that the difi'erence 
in untaiiped trees is due to the same cause as the difference in trees that have been tajiped. As 
stated above, the cause of the dift'erence among tapped trees can not be traced directly to 
tapping; it ought to be looked for, rather, in the condition of the trees previous to tapping. 

The difference between trees 52 and 53 can be exjilained on the following hypothesis : 53 had 
been a rich tree from early growth and had a large amount of tnrpentine stored up in the heart- 
wood; 52 for some reason or other had very little stored away. When the two trees were sub- 
jected to tapping they gave up whatever turpentine they had in the sapwood and whatever they 
could produce from season to season, till at the end of four years the production became too small 
in amount and too jioor in quality. Tlie trees were then abandoned. But tree No. 53 had its 
oleoresin in the heartwood untouched, while No. 52 had hardly any before tapi)ing, and for the 
same unknown cause did not store away any in the heartwood after the tree had been abandoned. 



RESIX IN I3I>ED AND UNBLED TREES. 343 

Tlie explanation offered in the i>recediiig paragraph gains still more probability wb en trees 60 
and 01 are compared with each other and also with 52 and 53. The difference between 1 and 2, the 
results of average analyses — all these are very suggestive of the theory tliat the sap, and not the 
heart of the tree, supplies the turpentine when the tree is tapped. The fact that the heartwood of 
trees felled one year after tapping is fully as rich or as poor as that of trees felled five years after 
tapping, seems to the writer of especial significance, for it shows that the richness of the heart- 
wood in a tapped tree is independent of time of rest before felling. 

It is a well-known fact that when a pine tree is cut transversely, liquid turpentine immedi- 
ately appears on the fresh su:face of the sa]iwood, while the heartwood remains perfectly clear. 
It would seem as if the turpentine in the sap is far less viscid than that in the heart of a tree. It 
is probable that the turpentine in the sap is richer in volatile hydrocarbons than that in the heart. 
(A difference of cell structure and manner of existence of oleoresins may also account for this 
difference in part. — B. li. F.) 

It is generally stated that crude turpentine as obtained on a large scale yields from 10 to 25 

T 
per cent of volatile oil. This gives p-= 11.11 to 30, with an average of over 20. This average 

T 
is somewhat iiishcr than that for the ,, as found for the turpentine from heartwood of the 21 

trees analyzed. Although experimental data are wanting to show conclusively that the difference 

in the consistency of tlie oleoresin from sapwood and heartwood is due to a difference in the 

relative amount of volatile oil, yet it is quite probable that this should be the cause. The oleoresin 

in the heartwood of trees has been produced for the most part when the "heartwood was yet 

sa])wood. Therefore that part of turpentine which is found in the heartwood is the oldest in age 

and consequently has been exposed the longest to oxidizing influences of air, which gradually 

replace the water when the sapwood changes to heartwood. It is the same kind of oxidation and 

of thickening which takes place when crude turpentine is exposed to the air and sun, or when a 

T 
fresh cut is made in the bark of a tree. It is probably for the same reason that ,, becomes smaller 

as we approach the pith of the tree, because the parts nearest the pith are the oldest. 

It is difficult to conceive how the thick oleoresin of the heartwood could be made to flow 
toward the incision when a tree is tapped. It is also difficult to explain by what means tfie tree 
could change this thick turpentine into a less viscid solution in order that it may flow toward the 
wound. 

One would Judge, a priori, from the great difference in the consistency of the turpentine in the 
heart and sap that only the liquid turpentine will flow when a tree is tapped. Tapping will then 
have little effect, if any, upon the oleoresin stored up in the heartwood of the tree. A tree whose 
heartwood is rich in turpentine will remain so after tapping. 

The writer is not willing to generalize too hastily from so few results and consider them as a 
solution of the problem. A large number of analyses, devoid of the possibility of chance selection 
of samples, is necessary before a positive or a negative answer can be given to the question, does 
the tapping of trees for turpentine affect the subseciueiit chemical composition of the heartwood? 

But, however few in number the results are, they admit of the following conclusions: 

(1) Trees that have been tapped can still contain very much turpentine in the heartwood. 

(2) Trees that have been abandoned for only one year before felling can contain fully as much 
turpentine iu the heartwood as trees that have been abandoned for five years. 

(3) Trees that have not been tapped at all do not necessarily contain more turpentine in the 
heartwood than trees tliat have been tapped. 

The following diagram serves to show what proportion of each disk was involved in each of 
the detail analyses, and the results in each case. The right-hand vertical line represents the pith 
of the tree, the horizontal lines represent the radical extension of each disk, as numbered by romau 
number, the position of the disk in the tree being maintained as in nature, IV being the top, II 
the lower, and III the intervening disk. The subdivisions of radii represent the actual divisions 
of the disk to scale of one-half natural size, the portions to the left of the heavy subdivision line 
representing sapwood s 1 and s 2; the portions to the right heartwood /(, /*, divided according to 
the method as indicated above. The fonr columns.of figures over ea('h disk piece represent results 
pertaining to that piece; they stand in order from the toi) for (1) mimber of rings, (2) volatile 



344 



FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



T 
hydrocarbons, (3) rosin, (4) ratio „; (2) and (3) a.s calculated on wood free from moisture. 

instance, for tree No. 53, disk IV, .s2, we find — 



For 



40 = Nuiu1)er ol" riiiss. 
0.40 = Per cent of volatile hydrocarbons. 
3. 81=: Per cent of roHiii. 
T 



10.37 = 



R' 





40. 






30, 




34 






33 




31. 


35. 




0.40 






tl, 4(1 




4 


56 




4 


49 


3.86 


2.66 




3.81 






3, '.It; 




24 


01 




22 


23 


17.74 


15.19 


Tree 


1 10. 37 






11.60 


1 


19 


02 


1 


20 


12 


1 21.77 


1 17.53 


No. 53. 


40. 


37 






35. 






38. 






30. 


18. 




0.39 





42 




3.87 






3.81 






2.10 


1.2;» 




2.90 


3 


OS 




21.77 






20.09 






11.97 


il.71 




1 13.01 1 


13 


82 


1 


17.85 




1 


18.94 




1 


17.53 


1 13, 10 


w. 


40. 








33. 






32. 






32. 


28, 


U.18 


0,19 








2.56 






4.39 






2.22 


1,46 


0.97 


0.96 








12.02 






24.70 






12.30 


8.96 


1 18.39 


1 19.77 






1 


21.23 




_L 


22.43 




1 


18.29 


1 16. 33 



IV. 



III. 



II. 









40. 






35. 


32. 




34. 






30. 




30. 










0.26 






0.34 


0. 


15 


0.22 






0.23 




0.26 










1.40 






1.34 


1. 


05 


1.97 






1.72 




1.92 




Tree 


No. 52 


40. 


18,78 




1 


25.20 


1 9.33 


11.11 




1 


13.38 


1 


13,64 




30. 


30. 








30. 




32. 






27. 






11, 


0.25 




0,25 


0. 


15 






0.20 




0.14 


» 




0.18 






0.18 


1.99 




1,87 


1. 


77 






1.87 




1.86 






1.60 






1.53 


1 12.71 


1 


13.67 


1 8.64 




1 


10.51 




1 7.85 






9.05 




1 


9.26 


40. 




40. 




36 






32 






35 






24 






0.30 




0.31 







30 




U.26 







17 







17 




2.19 




2.01 




2 


17 




1 


83 




1 


98 




1 


51 




1 13.64 


1 


13.48 


1 


14 


14 




1 14 


38 


1 


8.83 


1 


II 


60 





Tree 
No. 61. 



30, 


36. 


40. 


33. 


35. 


30. 


0,22 


0.28 


3.07 


3.49 


3.14 


1.08 


3.01 


2.75 


13.55 


16.29 


14.18 


8.04 


1 7.35 


10.20 


1 22.05 


1 21.42 


1 21. 42 


1 13.39 


35. 


35. 


36. 


33. 


30. 


35. 


0,20 


0.26 


1.57 


2,09 


2,92 


0.75 


3.01 


3.11 


7.8H 


13,57 


11. 34 


5.67 


1 C, ,50 


1 8, 36 


1 19.85 


1 19, 86 


1 25. 81 


1 13. 28 



II. 



Tree No. 60. 





30. 




27. 






28 






30. 






40. 










0.16 




0.24 









84 




0.41 
















2.32 




2.66 






5 


35 




3.13 














1 


7.02 


1 


9.09 




1 


15 


.59 


1 


12. So 




1 










30. 




34. 






30. 






36. 






36. 








20. 


0.28 




0.35 






0,58 






0. 40 






0.42 








0.50 


2.65 




2,88 






3, 60 






2.99 






2.42 








3. 39 


1 10.33 


1 


12.16 




1 


15.27 




I 


13,23 


1 




17.04 




1 




14.70 


30. 


35. 






37. 






33. 




35. 








27. 






0.29 


0.33 






0.71 






0. 


51 


0. 


73 






0.47 




2.28 


2.63 






5. 03 






2. 


71 


5. 


19 






3. 


62 




1 12.74 


1 12. 56 




1 


14.07 


1 




18. 


62 1 


14. 


03 




1 


13. 


00 





Tree No. 1 . 





30. 


28. 


32. 




19 






0.22 


0.25 


1. 


)7 


1 


06 




1.43 


1.57 


7.61 


6 


62 


1 


15.27 


15. 97 1 


14. 


12 


16 


04 


30. 


33. 


30. 




25. 




13. 


0,32 


0.34 


0.94 




0.73 




0.40 


2,25 


2, 25 


4.90 




5,12 




3.57 


1 14. 49 


1 13. 90 


1 19. 11 




14,21 


1 


11.20 


30. 


35 


35. 


34. 






15. 


0.20 


0,17 


0,18 


0.66 






0..37 


1.06 


1,32 


6,57 


3.92 






2.23 


18.55 1 


13.72 1 


17.97 1 


16.67 




1 


16. 50 









30. 


36. 


30. 


30 












0.31 


0.34 


1.13 





87 










2.62 


2.71 


8.10 


6 


41 








1 


12.12 


12. 36 1 


13.98 


13 


53 






30. 


36. 


33. 


28, 




17. 








0.18 


0.24 


1.37 


0.92 




0, ,S6 








1.95 


2.24 


9.14 


5,89 




7.40 




Tree No. 2. 


1 


8.94 1 


10,06 


1 14.77 


1 15.61 


1 


11.64 




30. 


26. 


34. 




30. 


30. 






11. 


0.20 


0.31 


1.55 




1.93 


1.39 






1,10 


4,29 


3.05 


10.10 




14.19 


8.78 






8,04 


1 4.58 


1 10. 00 


1 15. 35 


1 


14.4 


1 15, 75 





1 


12.99 



III. 



II. 



IV. 



III. 



II. 



FiQ. 90.— Diagram of detail analyses, representing radial dimensions of test pieces in each disk. Scale, onelialf natural size. 



DISTRIBUTION OF RESINOUS CONTENTS. 



345 



Table I.— TREE No. 53. 





Part of 
disk. 


Number of 
rings. 


Width. 


Water. 


Volatile 
liydro- 
ciu-boH. 


Ko.'^in. 


Calculated ou wood free 
from moisture. 


Vol. hydroc. 




Volatile 
hydro- 
carbon. 


Ko.siu. 


No. of ili.sk. 


Rosin, '-'l"" 


II 

Ill • 

IV 


Is 
2s 
III 
2A 
3A 
ih 
U 
2e 
1ft 
2A 
3/1 
4A 
Is 
2s 
lA 
2h 
3/1 
ih 


37 
40 
33 
32 
32 
28 
40 
37 
35 
38 
30 
18 
40 
30 
34 
33 
31 
15 


Vm. 
3.3 
4.0 
3.0 
2.9 
5.0 
10.0 
2.7 
2.6 
3.5 
4.1 
5.5 
7.0 
4.0 
3.0 
3.9 
3.0 
5.8 
6.3 


Per cent. 

10. 51 
10. 05 
9.1] 
8.79 
8.47 
*11.23 
9.08 
8.90 
7.89 
8.04 
8.55 
8.79 
8.96 
8.67 
8.04 
7.93 
8.65 
9.-55 


Per cent. 
0.16 
0.17 
2.32 
4.00 

2. 03 
1.30 
0.35 
0.38 
3.57 

3. 50 
1.92 
1.14 
0.30 
0.42 
4.20 
4.13 
3.53 
2.41 


Per cetit. 

0.87 

0.86 

10. 93 

17. 83 

11.26 

7.96 

2.69 

2.75 

20. 05 

18.48 

10.95 

8.86 

3.47 

3.62 

22.08 

20.56 

16.21 

13.74 


Per cent. 
0.18 
0.19 
2.56 
4. 39 
2.22 
1.46 
0.39 
0.42 
3.87 
3.81 
2.10 
1. 2;-. 
0.40 
0.46 
4.50 
4.49 
3.86 
2.66 


Per cent. 

0.97 

0.96 

12. 02 

24. 70 

12,30 

8.96 

2.96 

3.02 

21.77 

20. 09 

11.97 

9 71 

3.81 

3.96 

24.01 

22. 33 

17.74 

15.19 


18.39 
19.77 
21.23 
22.43 
18.29 
16.33 
13.01 
13.82 
17.85 
18.94 
17.53 
13.10 
10.37 
11.60 
19.02 
20.12 
21.77 
17.53 



*53, II, 4ft has been analyzed some three weeks earlier than the remaining parts of this tree, hence a large per cent of moisture. 



Table II.—TREE No. 52. 





1< 


40 


3.1 


9.72 


0.27 


1.98 


0.30 


2.19 


13.64 




2» 


40 


3.9 


9.77 


0.28 


1.81 


0.31 


2.01 


15.47 


II 


Ih 


36 


4.6 


8.67 


0.28 


1.98 
1.08 


0.30 


2.17 
1.83 


14.14 




















3h 


35 


6.8 


8.80 


0.16 


1.81 


0.17 


1.98 


8. 83 




ih 


24 


7.4 


8.55 


0.16 


1.38 


0.17 


1.51 


11.60 




U 


30 


3.0 


9.12 


0.23 


1.81 


0.25 


1.99 


12.71 




2s 


40 


3.5 


9.00 


0.23 


1.68 


0.25 


1.87 


13.67 




1/i 


30 


3.4 


8.44 


0.14 


1.62 


0.15 


1.77 


8.64 


III 1 


2/1 
3/1 


30 
32 


3.0 
4.8 


8.51 
8.37 


0.18 
0. 13 


1.71 
1.70 


0,20 
0.14 


1.89 
1.86 


10.51 




7.65 




ih 


27 


6.9 


9.35 


0.14 


1.45 


0.15 


1.60 


9.65 




ih 


11 


.5.0 


9.21 


0. 13 


1.39 


0.14 


1.53 


9.26 




U 


40 


3.5 


8.88 


0.24 


1.28 


0.26 


1.40 


18.78 




2s 


35 


3.3 


8.49 


0.31 


1.23 


0.34 


1.34 


25. 20 


IV < 


U 


32 


3.0 
2.8 


9.08 


0.14 


1.50 


0. 15 


1.65 
1.97 


9.33 
11.11 


















3/1 


30 


3.6 


8.48 


0.21 


1.57 


0.23 


1. 72 


13.38 




ih 


30 


6.8 


8.10 


0.24 


1.76 


0.26 


1.92 


13.64 



Table III.— TREE No. 61. 





Is 


35 


3.0 


7.94 


0.18 


2.77 


0.20 


3.01 


6.50 




2» 


35 


3.0 


7.90 


0.24 


2.87 


0.26 


3. 11 


8. 36 


II 1 


l/i 


36 


2.8 


7.35 


1.45 


7.30 


1.57 


7.88 


19. 85 


2/j 


33 


3.2 


7.58 


2.49 


12.54 


2.69 


13.57 


19.86 




3/1 


30 


4.5 


7.64 


2.70 


10.46 


2.92 


11.34 


25.81 




4/1 


35 


9.5 


7.10 


0.70 


5.27 


0.75 


5.67 


13.28 




1« 


30 


3.0 


7.65 


0.20 


2.78 


0. 22 


3.01 


7.35 




2» 


36 


2.7 


7.43 


0.20 


2.55 


0.28 


2.75 


10.20 


III I 


l/i 


40 


3.1 


7.14 


2.85 


12.58 


3.07 


13.55 


22.65 


2/i 


33 


3.2 


7.46 


3.23 


15.08 


3.49 


16.29 


21.42 




ah 


35 


6.0 


7.41 


2.91 


13.59 


3.14 


14.18 


21.42 




ih 


30 


8.0 


7.09 


1.00 


7.47 


1.08 


8.04 


13.39 



Table IV.— TREE No. 60. 





1* 


30 


2.7 


9.91 


0.26 


2.04 


0.29 


2.26 


12.74 




2s 


35 


2.8 


9.34 


0. 30 


2.39 


0.33 


2.63 


12. 56 


n 


l/i 


87 


3.5 


8.72 


0.65 


4.62 


0.71 


5,03 


14.07 


2/. 


33 


4.5 


9.15 


0.46 


2.47 


0.51 


2.71 


18. 62 




3/1 


35 


4.6 


8.01 


0.67 


4.71 


0.73 


5.19 


14. 02 




4/1 


27 


6.5 


8.45 


0.43 


3.31 


0.47 


3.62 


13,00 




Is 


30 


3.1 


8.74 


0.25 


2.42 


0.28 


2.65 


10.33 




2s 


34 


2.8 


8.60 


. 0.32 


2.63 


0.35 


2,88 


12.16 


Ill 


l/i 


30 


3.2 


8.68 


0.,53 


3.47 


0.5B 


3.80 


15.27 


2/1 


36 


4.4 


9.02 


0.36 


2.72 


0,40 


2.99 


13.23 




3/1 


30 


4.5 


7.73 


0.38 


2.23 


0.42 


2.42 


17.04 




4/1 


20 


6.0 


7.73 


0.48 


3.13 


0.50 


3.39 


14.70 




Is 


30 


2.6 


7.51 


0.15 


2.15 


0.16 


2,32 


7.02 




2s 


27 


2.6 


7.84 


0.22 


2.45 


0.24 


2.66 


9.09 


IV 


Ih 


28 


3.7 


7.77 


0.77 


4.94 


0,84 


5.35 


16.59 




2/1 


36 


5.0 


8.12 


0.37 


2.88 


0.41 


3.13 


12.86 




3/1 


40 


8.0 


7.92 


0.26 


2.81 


0.28 


3.05 


9.18 



346 



FORESTKY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



Table v.— TREE No. 1. 

















Calculated on woed free 


















from moiature. 




No. ..f.liak. 


Part of 
disk. 


Number ef 
ringa. 


Width. 


Water. 


Tolatilo 
liydro- 
carlion. 


Rosin. 


Volatile 
hydro- 
carbon. 


Rosin. 


Vol. hydroc'. 
Rosin. ■ '"" 








Cm. 


7Vr cent. 


J't-r cent. 


Per cent. 


Per cent. 


J'er cent. 






l8 


30 


2.0 


8.67 


0. 18 


0.97 


0.20 


1.00 


18.55 




2» 


35 


3.0 


8.77 


0.10 


1.21 


0.17 


1.32 


13.72 


II J 


\h 


3.-. 


3.6 


8.5U 


1.08 


6.01 


1.18 


6.5T 


17.97 




2/1 


34 


fi.5 


8.39 


0.60 


3.6<l 


0. 06 


3.92 


16.67 




■Ml 


U 


3.0 


7.67 


0.34 


2.06 


0.37 


2.23 


16.50 




Is 


30 


2.8 


7.94 


0.30 


2.07 


0.32 


2.25 


14.49 




'Js 


33 


3.0 


7.92 


0.31 


2.23 


0.34 


2.42 


13.90 


III 


lA 


30 


3.8 


8.13 


0.86 


4.50 


0.94 


4.90 


19.11 




2A 


25 


4.2 


7.78 


0.67 


4.72 


0.73 


5.12 


14.21 




■Ml 


13 


3.5 


7.57 


0. 37 


3. 30 


0.40 


3. .I? 


11.22 




Is 


30 


2.2 


X. 33 


0. 20 


1.31 


0. 22 


1.43 


15. 27 


IV 


2» 


28 


2.8 


8.12 


0.23 


1.44 


0.25 


1. .17 


15.97 


Ml 


32 


5.0 


7.94 


0. 99 


7.01 


1.07 


7.61 


14.12 




•21, 


19 


5.2 


7.73 


0.98 


6.11 


1. 06 


6. 62 


16.04 



Table VI.— TREE No. 2. 





i.« 


30 


3.0 


7.65 


0.18 


3.95 


0.20 


4.29 


4.56 




2* 


20 


2.7 


8.19 


0.2S 


2.80 


0.31 


3.05 


10.00 


II 


lA 


34 


3.5 


7.31 


1.44 


9. 25 


1.55 


10.10 


15.35 


•ih 


30 


5.0 


8.11 


1.77 


13. or. 


1.93 


14.19 


14.41 




■Jli 


30 


6.0 


8.16 


1.27 


8.06 


1.39 


8.78 


15.75 




4k 


11 


4.2 


7.88 


1.07 


8.24 


1.16 


8.94 


12.99 




la 


30 


2. 7 


8.00 


0.16 


1.70 


0.18 


1.95 


8.94 




2s 


36 


3.0 


8.01 


0.22 


2. 116 


0.24 


2.24 


10.06 


m 1 


l/i 


33 


3.2 


7.44 


1.25 


8.40 


1.37 


9.14 


14.77 




2A 


28 


5. 5 


7.78 


0. 85 


5.44 


0.92 


5.89 


15.61 




3li 


17 


4.8 


7.12 


0.80 


6.87 


0.86 


7.40 


11.84 




1« 


30 


2. 7 


8.20 


0.28 


2.31 


0.31 


2. .52 


12.12 


IV 


2s 


36 


3.0 


8.08 


0.31 


2. 49 


0.34 


2.71 


12. .36 










8.10 














271 


30 


7.6 


7.81 


0.80 


5.91 


0.87 


6.41 


13.53 



Table VII— Si'MMAet of Results op Trees Nos. 54 to 69 and Nos. 17 to 19. 



Serial number of trees. 



Part of disk. 



54, 55, 56, 57 . . 
58, 59 

63.64,05 

00, 67. 68, 60 . . 
17,18,19 






2/1/ 



Disk II. 



Volatile hy- 
drocarbons. 



^} '■ { 



0.18 
1. 161 

0. 70/' 
0.28 
0.80 
0.18 
0.811 

1. 00/' 
0.14 
0. 80 
0.1-1, 
0.781 
0. 50/ 



Rosin. 



Per cent. 
1.48 

4.97/-''''' 

1.76 

4.06 

1.74 

4. 3:i\- .,,, 

6. 29r- ■'- 

1.78 
4. 95 
1.49 

2. 4?}" "8 



Vol.hydr. 



Rosin. 



14 

14\,.. 

oil'''" 

76 

63 

00 

5''U7 
80j"- 

00 

00 

56 



Volatile hy- 
drocarbons. 



Per cent. 
0.26 
0.811 
0.34;" 
0. 20 
0.82 



0. 58 



Rosin. 



Per cent. 
1.03 

|:«2}3.89 

1.35 

4.29 



Vol.hydr. 
Rosin. 



13.33 

5?:«?}i4.o4 

14.14 
19.10 



1.34 

f 0.91U .J. I 3.03^3 ,, 
\ 0.5or- " 1 2, 79/-'-"' 



8.20 
25.15\,, -J 

18. 36;-'-''' 



Timber Physics Work. 

The timber physics work was continued actively antl the investigation extended to other kinds 
of timber, both conifers and hard woods. In 189G the Division was in position to announce its 
findings with regard to the mechanical, physical, and structural study of the four principal Southern 
pines (Circular ll'). Ikiscd, as these results are, on over 20,000 mechanical tests and over 50,000 
weighings and measurements, they may fairly be regarded as tinal, and thus avoid future discus- 
sion and much fruitless and expensive private testing. According to this exhaustive study, the 
Cuban and long-leaf pine rank foremost among our timber pines, and are fully 20 to 25 per cent 
stronger than had previously been assumed. It also appeared that the wood of these species 
varies in strength directly as the weight (little discrepancies being well accounted for by varia- 
tions in resin contents, which add only to weight and not to strength); that in the same tree the 
wood varies according to certain definite laws, being heaviest at butt, lightest in top, heavier in 
the interior, and lighter and weaker in the outer parts of saw-size timber; that thus the age when 
formed, as well as the position in the tree, exercises a definite influeiice which is generally far 
greater than the mu(^h-(iuoted influences of soil, locality, etc. In this latter respect it was clear 



TIMBER PHYSICS SOUTHERN PINE. 347 

from the results that the oft-claimed superiority of the timber of certain localities is not 
substantiated by experiment, but that there is heavy and strong as well as lighter and weaker 
timber in every locality throughout the range of these species. The all-important efiect of 
moisture was carefully considered throughout the work, and it was established that in general 
an increase in strength of at least 50 to 75 per cent takes place during ordinary seasoning, so that 
for all designing of covered work, as in ordinary architecture, this improvement may be depended 
upon and considered in the proportioning of the timbers. 

The manner in which the valuable information was secured and communicated will appear 
from the following reprint of Circulars 12 and 15, issued in 1896 and 1897: 

Southern Pine — Mechanical anh Physical Properties. 

IMIE MATKKIAL HXIiEI! considf.ration. 

The importance of reliable informatiou regariliug the pines of the South is evident from the fact that they furnish 
the bulk of the hard-pine material used for constructive purposes with an annual cut hardly short of 7,000,000,000 
feet B. M., which, with the decline of the soft-pine supplies in tlie North, is bound to increase rapidly. 

Although covering the largest area of coniferous growth in the country (about 230,000 square miles), proper 
economies in their use are nevertheless most needful, since much of this area is .already severely culled and the cut 
per acre has never been very large. Ilenee the demonstration (a result of the iuvtstigations in this Division) that 
bled pine is .as strong and useful as unUled, and the .assurance that long-leaf pine is in the average 2.^ per cent 
stronger than it is often supposed to be, and therefi>re can be used in smaller sizes tlian customary at present, must 
be welcome as permitting a saviug in fonst resources which may readily be estimated at from eight to ten million 
dollars annually, due to this information. 

The pines under consideration, often but imperfectly distinguished by consumers in name of substance, .are: 

(1) The long-leaf pine { I'iniia jiahiatris), also known as Georgia or yellow jiine, and in England as "pitch 
pine," and by a number of other names, is to bo found in a belt of 100 to 150 miles in width along the Atlantic and 
Gulf coasts from North Carolina to Texas, furuishing over i^O per cent of the pine timber cut in the South — the 
timber par excellence for heavy construction, but also useful for flooring and in other directions where strength .and 
wearing qualities are required. 

(2) The Cuban pine (Pinus heteropht/lla), found especiiilly in the southern portions of the long-leaf pine belt, 
known to woodsmen commonly .as "slash pine," but not distinguished in the lumber market. It is usually mixed in 
with long leaf, which it closely resembles, although it is wider ringed (coarse grained), and to which it is eijual if 
not superior in weight and strength. 

(3) The short-leaf pine (Piiiiis ecldnnta), also known, besides many other u.ames, as yellow pine and as North 
Carolina pine, but growing through .all the Southern States generally north of the long leaf pine region; much 
softer and witli much more sapwood than the former two, useful mainly for small dimensions and as linishiug wood, 
being about 20 per cent weaker than tlio long-leaf pine. 

(4) The loblolly or old-fielil pine ( I'iuiis tada), of similar although more Soutlieru range than the short leaf, also 
known .as Virginia jiiue, much used locally and in Wasiiiugtou and Baltimore, destined to find more extensive 
application. At present largely cut together with short leaf and sold with it as "yellow pine," or North Carolina 
pine, without distinction, although sometimes far superior, approaching long-leaf pine in strength and general 
qualities. 

The names in the market .are often used interchangeably and the materials in tlie y.ard mixed. All four species 
grow into tall but slender trunks, as a rule not exceeding 30 inches in diameter and 100 leet in height; the bulk of 
the logs cut at present fall below 20 inches. The sapwood forms in old trees of long leaf (with 2 to 4 inches) about 
40 per cent of the total log volume ; in Cuban, short leaf, and loblolly 60 per cent and over. 

A reliable microscopic distinction of the wood of the four species has not yet been found. As a rule long leaf 
contains much less sapwood than the other three. The narrow-ringed wood of long leaf (.averaging 20 to 2.5 rings 
to the inch) usually separates it also from the other three, while the especially broad-ringed Cuban excels usually 
also by broader summer-wood bands. In the log short leaf and loblolly may usually be recognized as distinguished 
from the former by the gre.ater projiortion of sapwood and lighter color due to smaller proportion of summer wood. 
The general appearance of the wood of all four species is, however, quite similar. The annual rings (grain) are 
sharply detined; the light ycdlowish spring wood and the dark orange-brown summer wood of each ring being 
strongly contrasted produce a pronouuced piitteru, %vhieh, .although pleasing, especially in the curly forms (which 
occur occasionally), may become obtrusive when massed. 



348 



FORESTRY INVESTIGATIONS V. S. DEPARTMENT OF AGRICULTURE. 



TUo following diagnosis may prove helpful iu the ilistinctiou of tho wooil : 

Diagnostic features of the wood. 



Name of species. 


Long-leaf pine (P'mus 


Cuban pine {Pinus 


Short-leaf pine {Pinus 


Loblolly pine {Pinus 
^trta'Linn.). 


palugtris Miller). 


heterophylla (VAX) .Sud). 


evhinata Miller). 


Specific gravityol'kiIn-/l*o3siblP range 


. r.0 to . 90 


. no to . 90 


. 40 to . 80 


.40 to. 80 


dried wood. (Moslfrequi'iitrangH. 


. 55 to . C5 


. 55 to . 70 


. 45 to . 55 


. 45 to . 55 


Weight, poiiuds per cubic loot, kiln-dried 












3C 


?>! 


30 


31 


Charatter of grain Been iu cross eeotiun 


Fine and even; annual 


Variable ami coarse. 


Very variable; me- 


Variable, mostly very 




rings quite uu i- 


rings mostly wide; 


dium, coarse; rings 


coarse; 3 to 12 rings 




foriuly iKirrow; on 


averaging on large 


wide near heart, iol- 


to the inch, gener- 




large logs averag- 


logs Hi to 20 rings to 


lowed by zone of 


ally wider than iu 




ing generally 20 to 


the inch. 


narrow rings; not 


the short leaf. 




'jr> rings to the inch. 




less than 4 (mostly 
about 10 to 15) rings 
to the inch, but 
often very fine 
grained. 




Color, general appearance 


Even tlark reddish 


Dark straw color wit h 


Whitish to reddish or 


Yellowish to orange 




yellow to reddish 
ijrown. 


tinge ol tlesh color. 


yellowish brown. 


brown. 












Little; rarely overs to 
3 inches of radiuft. 


liroad ; 3 to 6 inches . . 


Commonly over 4 
inches of radius. 


Very variable, 3 to 6 






inches of the radius. 




Veryabundant; parte 

often turning into 


Abundant, sometiuiea 
yielding more (litch 


Moderately abundant, 

least pi"t(!hy; only 


Abundant; more than 




short leaf, less than 




•'light wood;" 


tlian long leaf; 


near atuuips, knots. 


long leaf and Cuban. 




pitchy throughout. 


"bleeds" freely, 
>■ i e 1 d i n g little 
'scrape. 


and liuiba. 


but does not ' ' bleed " 
if tapped. 



The sapling timber of all four species is coarse grained, that of loblolly exceeding the rest in this respect. 
The grain varies most in the butt, least in the top, is very fine in the outer jtortions of all old trees. Loblolly in the 
center of the log frequently shows rings over one-half inch wide, .and timber av<'ragiug eight rings to the inch is 
not rare, while short leaf will average 10 to 1.^ rings to the inch. The greater or less proportion of the sharply 
defined darli-colored bands of summer wood of the ring furnish the most reliable and re.ady means of determining 
quality. 

At present distinction is but rarely made in the species and in their use. All four species are used much alike, 
although difl'erentiation is very desirable on account of the difi'ereuoe in (juality. Formerly these pines, except for 
local use, were mostly cut or hewn into timbers, but especially since the use of dry kilns has become general and 
the simple oil linish has displaced the unsightly painting and "graining" of wood Southern pine is cut into every 
form and grade of lumber. Nevertheless, a large proportion of the total I'ut is still 1)eing sawed to order iu sizes 
above ti by (i inches, and lengths above 20 feet for timbers, for which the long leaf and Cuban furnish ideal mati'rial. 
The resinous condition of these two pines make them also desirable for railway ties of lasting quality. 

MECHANICAL PROPERTIKS. 

In general the wood of .all these pines is heavy for pine (31 to 40 pounds per cubic foot, when dry); soft to 
moderately hard (hard for pine), requiring about 1,000 pounds per sqnare inch to indent one-twentieth inch ; stifi', 
the modulus of elasticity being from 1,,")00,000 upward; strong, requiring from 7,000 pounds per sipiare inch and 
upward to break in bending, and over 5,000 pounds in compression when yard-dry. 

Thi' values given in this circular are averages based on a, Large number of tests, from which only defective 
pieces are excluded. 

In all cases where the contrary is not stated the weight of the wood refers to kiln-dried material and the 
strength of wood containing 15 per cent moisture, which may be conceived as just on the border of air-dried 
condition. The first table gives fairly well the range of strength of commercial timber. 

Average strength oj Soutlieni inne. 
Air-dry material (abuut IJ per cent moisture). 



Name. 



Compression streugth. 



Witli grain. 



Avei-age 

of all valid 

tests. 



Across 
Average grain. 

'for the weakest, 3 per cent 
oue-teuth iudeuta- 

ol' all the tests. lion. 



Absolute. 



Rela 



Absolute, 



Rela- 



Bending strength. 



At rupture 

modulus f )y' 
2 bIC 



Average 

of alt valid 

testa. 



Average 
Ifor the weakest modulus 
I one-tenth | 3 W.i 
'of all tlie teats., '2bh^ 



At elastic Elasticity 

limit (stiflness) 

modulus 



Absolute. Ke^- Absolute. R*- 



3 \VP 

4 A ill' 



Relative 

elastic 
resili- 
ence. 



Tensile Shearing 
streugth. strength. 



I Lbs. per 
«(/. inch. 

Cuban pine | 7,850 

Longleaf pine..| 6, 85C 
Loblolly pine.. e,5U0 
Sborlleaf pine . 5,900 



Lbs. per 
«</. inch. 
6,500 
5.650 
5,350 
4, 8UU 



Lbs. -per 

sq. inch. 

1,050 

1,060 

990 

040 



Lbs. per 
gfj. inch. 
11,950 
10,900 
10, 100 
9,230 



Lbs. per 



sq. 



Itch. 
8,750 
8,800 
«. 100 
7, 000 



Tjbs. per 
Kq. inch. 
9,450 
8,600 
8,150 
7, 200 



JAg. per 
sq. inch. 
2, 305, 000 
1, 890, 000 
1, 950. 000 
1,600,000 



In.-lbs. 
per en. in. 
2.5 
2.3 

2. 05 



Lbs. per 
sq. inch. 

14, 3U0 

15, 200 
14. 400 
13,400 



Lbs. per 
sq. inch. 
680 
706 
690 
688 



TIMBER PHYSICS SOUTHERN PINE. 



349 



HELATION OF STRENGTH TO WEIGHT. 



The intimate relation of strength ami specific weight has been well established by the experiments. The aver- 
age results obtained in connection with the tests themselves were as follows: 



Transverse strenstli 

Specific weight of test pieces. 



Cuban. 



100 
100 



Longleaf. 



91 

94 



Loblolly. 



84 
82 



Since in the determination of the specific f;ravity above given, wood of the same j)er cent of moisture (as is the 
case of the values of strength) was not always involved, and also since the test pieces, owing to size and shape, can 
not perfectly represent the wood of the entire stem, the following results of a special inquiry into thi; weight of the 
wood represents probably more accurately the weight and with it the strength-relations of the four species. 

WEIGHT KEI.ATIONS. 
[These data refer to the average ai)eciiic weight for all the wood of each tree, only trees of approximately the same age being involved.] 



Average .ige ()f trees 

Number of trees involved... 
Specific gravity of dry wood 

Weight per cubic loot 

Relati V(> weight 

(Transverse strength a) 



Cuban. 



171 
6 

0.63 
39 
100 
(100) 



Longleaf. 



127 

22 
0.61 

38 

97 
(91) 



Loblolly. 



i:i7 

14 
0.53 
33 
84 
(84) 



Shortleaf. 



131 

10 
0.51 

32 

81 
(77) 



a The values of strength refer to all tests and therefore involve trees of wide range of age and consequently of quality, especially 
those of longleaf, involve innch wood of old trees, hence tiio rehitiou of weight and strength appears less distinct. 

From these results, although slightly at variance, we are justified in coududiiig that Cuban and longleaf pine 
are nearly alike in .strength and weight aud excel loblolly and shortleaf by about 20 per cent. Of these latter, 
contrary to common belief, the loblolly is thc^ heavier and stronger. 

The weakest material would differ from the average material iu transverse strength by about 20 per cent and 
in compression strength by about 30 to 35 per cent, except Cuban pine, for which the difference appears greater 
in transverse and smaller in compression strength. It must, of course, not be overlooked that these figures are 
obtained from full-grown trees of the virgin forest, that strength varies with physical conditions of the material 
and that, therefore, an intelligent inspection of the stick is always necessary before applying the values in practice. 
They can only represent the average conditions for a large amount of material. 

DI.STHIISUTION OE WEIGHT AXD STHENGTH THKOl GHOUT THE TREK. 

In any one tree the wood is lighter and weaker as wo pass from the base to the top. This is true of every tree 
and of all four S])ecie8. The decrease iu w'eight aud strength is most pronounced in the first 20 feet from the stump 
aud grows smaller upwaril. (See lig. 91.) 

This great difference iu weight aud strength betwocu butt aud top finds explanation iu the relative width of 
the snmmerwood. Since the specific weight of the dark summerwood band in each ring is in thrifty growth from 
.90 to 1.00, while that of the springwood is only about .40, the relative amount of summerwood furnishes altogether 
the most delicate and acciiiato measure of these dift'crences of weight as well as strength, and hence is the surest 
criterion fur ocular inspection of quality, especially since this relation is free from the disturbing inlluoucu of both 
resin and moisture contents of the wood, so conspicuous iu weight detcrmiuations. 

The folliiwiug figures show the distribution of the summerwood iu a single tree of longleaf pine, as an example 
of this relation : 



At the .stnnip 

32 feet from stiunp 
87 feet from stump 



In the 10 
rings next 
to the bark 



Per cent. 
37 
25 
15 



In the 10 
rings, Nos. 

100 to 110 
from bark. 



7Vr ccjit. 
52 
36 
37 



Average 

for entire 

disk. 



3'er cent. 
SO 
33 
26 



Specific 
weight. 



0.73 
59 
55 



350 



FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



Weighl and strength of wood at different heights in the tree. 





Strength of loiifiloaf 
pine (pouudM por 
sqtiaro inch). 


Specific weight. 


Mejinof 
all three 
species. 
Jtelative 
weight. 


Relative 
strength of 

lou^leaf 
pine. 
Mean of com- 
pression and 

bendiug. 


Bending 
strength. 


Couiprea- 

siou end- 

wi.se 

(with 

grain). 


Longlcaf. 


I.obhdI.v. 


SliorlleaC. 




56 
150 (over) 


22 
127 


14 
113 


12 
131 


48 


56 


Average age of trees 




1 


1 1 

Number of feet from stump: 1 




.751 

106 

.705 

100 

.074 

06 
.624 

SU 
.600 

St 
.500 

SO 
.539 

77 
.528 

75 


.629 

106 

.595 

100 

.578 

07 
.534 

.90 
.508 

«6' 
.491 

SS 
.476 

SO 
.470 

79 


.614 

105 

.585 

100 

.565 

97 
.523 

90 
.496 

S5 
.472 

SI 
.455 

7« 
.454 

78 


1 

( 


1 


7,350 

urn 

7,200 

9S 

6,800 

as 

6,500 

sn 

6,300 
SO 

6, 150 
83 

6,050 
82 


lOG 




6 

10 


12, 100 

100 

11,650 


■ 100 
07 
00 
SS 
SI 
7.'< 
77 


im 
07 
90 
SG 
SI 
79 
76 


20 


or, 

10, 700 

S8 
10, 100 

SI 
9,500 

70 
9,000 

75 
8,600 

71 


30 


40 


50 


60 






30 
Feet from Stump. 

Fui. 91. — Variation of weight with height of tree. 



TIMBER PHYSICS SOUTHERN PINE. 



351 



60 fT 



Logs from the top can usiuilly be recognizeil liy the larger percentage of sapwood and the smaller proportion 
and more regular outlines of the bands of summer wood, which are more or less wavy in the butt logs. 

The variation of weight is well illustrated in the foregoing table, in which the relative values are indicated id 
italics. For comparison the figures for strength of loug-leaf 
pine are added. 

Both weight and strength vary in the different parts of 
the same cross section from center to perijjhery, and though 
the variations appear freciuently irregular in single individuals, 
a definite law of relation is nevertheless discernible in large 
averages, and once determined is readily observable in every 
tree. 

A separate inquiry, avoiding the many variables which 
enter in the mechanical tests, permits the following deduc- 
tions for the wood of these pines, and especially for long 
leaf, the data referring to weight, but by inference also to 
strength : 

1. The variation is greatest in the butt big (the heaviest 
part) and least in the tup logs. 

2. The variation in weight, hence also in strength, from 
center to periphery depends on the rate of growth, the heavier, 
stronger wood being formed during the period of most rapid 
growth, lighter and weaker wood in old age. 

3. Aberrations from the normal growth, due to unusual 
seasons and other disturbing causes, cloud the uniformity of th(v 
law of variation, thus occasionally leading to the formation of 
heavier, broad-ringed wood in old, and lighter, narrow-ringed 
wood in young trees. 

4. Slow-growing trees (with narrow rings) do not make 
less heavy, nor heavier, wood than thriftily grown trees (with 
wide rings) of the same age. (See fig. 92.) 

EFFECT OF AGE. 

The interior of the butt log, representing the young sap- 
ling of less than 15 or 20 years of age, and the central portion 
of all logs containing the pith and 2 to Ti rings adjoining is 
always light and weak. 

The heaviest wood in long-leaf and Cuban pine is formed 
between the ages of 15 and 120 years, with a specific weight of 
over 0.60 and a maximum of O.GG to ().G8 between the ages of 40 
and 60 years. The wood formed at the age of about 100 yc^ars 
will have a specific weight of 0.62 to 0.63, which is also the 
average weight for the entire wood of old trees. The wood 
formed after this age is lighter, but does not fall below 0.50 
up to the two hundredth year ; the strength varies in the same 
ratio. 

In the shorter-lived loblolly and short leaf the period for 
the formation of the heaviest wood is between the ages of 
15 and 80, the average weight being then over 0.50, with a 
maximum of 0.57 at the age of 30 to 40. The average weight 
for old trees (0.51 to 0.52) lies about the seventy-fifth year, 
the weight then falling oft' to about 0.45 at the age of 140, 
and continuing to decrease to below 0.38 as the trees grow 
older. 

That these statements refer only to the clear portions of 
each log, and are variably affected at each whorl of knots (every 
10 to 30 inches) according to their size, and also by thevarial)le 
amounts of resin (up to 20 per cent of the dry weight), must 
be self-evident. 

Sapwood is not necessarily weaker than heartwood, only 
usually the sai)wood of the large-sized trees we are now using 
is represented by the narrow-ringed outer part, which was 
formed during the old-age period of growth, when naturally 

lighter and weaker wood is made; but the wood formed during the more thrifty diameter growth of the first 
eighty or one hundred years — sapwood at the time, changed iuto heartwood later— was, even a.s sai>waod, the 
heaviest and strongest. 




Fia. 92.— Schematic section through stem of long loaf pine, 
showing variation of specific weight, with height, diame- 
ter, and age, at 20 (aba.), 60 (dcd), 120 (eece), 200 (fStS) 
years. 



352 



FORESTRY INVKSTIGATIONS U. .S. DEPARTMENT OK AGRICULTURE. 



liANCiK <)1' V.\I,l'KS I'OIl WKKiHT AND .-STRENGTH. 

Although the range of values for the individual tree of any given species varies from butt to top and from 
center to periphery by 1.5 to 'J5 per cent and occasionally more, the deviation from average values from one individual 
to another is not usually as great as has been believed ; thus of 56 trees of long-leaf pine, 42 trees varied in their 
average strength by less than 10 per cent from the average of all 56. 

The following table of weight (which is a direct and fair indication of strength), representing all the wood of 
the stem and excluding knots and other defects, gives a more perfect idea of the range of these values: 

Ilniiije of spcrifio weight wilh aye (kiln-dried wood). 
[To avoid fractious the values are multiplied by 100.] 



Number of trees involved . 
Trees over 200 years old . . . 

Trees 150-200 y'ear.s olil 

Trees 100-150 vears old 

Trees 50-100 years old 

Trees 25-50 years old 

Trees uuder 25 years old... 



Cuban. 



24 
61 
03 



61 
55 
51 



Long leaf. Loblolly 



96 

57 

50 

60.5 

62 

61 

55 



60 



50 
53 

53.4 
S3 

48 



Khort 
leaf. 



51 
55 
57 
53 



Though occasionally some very exceptional trees occur, especially in loblolly and short leaf, the range on the 
whole is generally within remarkably narrow limits, as appears from the following tabic: 

lianye of apecijic neiglil iu trees of the gome aije {qiproximalely; areragesfor whole trees. 
(.Specific gravity iiiiiltiplied by 100 to a\'oid fractious.] 



Name. 


No. of 

trees. 


Age 
(years). 


Single trees. 


Average. 




r 4 

I 5 
13 
10 
12 


150-200 
50-100 
100-150 
125-150 
100-150 


56 68 62 65 ... ... 


62.5 
60.9 
60. .5 
52.8 
50.8 






Lous-leaf piue 

Loblolly pine 

Short-leaf pine 


59 66 57 62 66 58 59 57 57 66 59 62 57 

51 51 53 51 55 5:i 54 55 55 53 

45 4.7 53 47 50 51 55 55 53 51 50 53 .. 



From this table it would a]ipear that single individuals of one species would a)ppr<)ximate single individuals of 
another species so closely that the weight distinction seems to fail, but iu large numbers— for instance, carloads of 
material— the averages above given will prevail. 



INFLUENCE OF LOCALITY. 

In both the Cuban and long-leaf i)ine the locality Wjhere grown appears to have but little influence on weight 
or strength, and there is no reason to believe that the long-leaf ])ine from one State is better than that from any 
other, since such variations as are claimed can be found on any lO-acre lot of timlicr in any State. But with loblolly, 
and still more with short leaf, this seems not to be the case. Being widely distributed over many localities difterent 
in soil and climate, the growth of the short-leaf pine seems materially inllucnced by location. The wood from the 
Southern coast and Gulf region, and even Arkansas, is generally heavier than the wood from localities farther north. 
Very li"ht and tine-graiued wood is seldom met near the southern limit of the range, while it is almost the rule in 
Missouri, where forms resembling the Norway pine are by no means rare. The loblolly, occupying both wet and 
dry soils, varies accordingly. 

INl'LUENCE OK MOI.STURE. 

This influence is among the most important; hence all tests have been made with due regard to moisture 
contents. Seasoned wood is stronger than green and moist wood. The difference between green and seasoned wood 
may amount; to 50 and even 100 per cent. The influence of seasoning consists iu (1) bringing by means of shrinkage 
about 10 per cent more fibers into the same s(iuare inch of cross section than are contained in the wet wood; (2) 
shriukin" the cell wall itself by about 50 per cent of its cross section, and thus hardening it, just as the cow skin 
becomes thinner and harder by drying. 

In the following tables and diagram this is I'ully illustrated. The values presented in these tables and 
diagrams are based on large numbers of tests and are fairly safe for ordinary use. They still require further 
revrsion, since the relations to density, etc., have had to bo neglected iu this study. 



TIMBER PHYSICS SOUTHERN PINE. 



353 



lujlucncc of moisture on stremjih. 



Avenii;e of ;il! valid tests. 


Relative vnlnes. 




Per cent 

of raoist- 

ure.a 


Cu- 
ban. 

8,450 
10, 050 
11,950 
15,300 
5,000 
6, dOO 
7,850 
9, 200 


"JeSr: 


Lob- 
lolly. 


Short- 
leaf. 




Per cent 
of moist- 
ure. a 


Cu- 
ban. 


Long- 

leaS 


Lob- 
lolly. 


Short- 
leaf. 


Aver- 
age. 


Bending strength 

Crnaliing endwise 


f 33 
1 20 

1 ^^ 

{ 10 

1 33 

•20 

15 

10 


7, 660 

8, 900 
10, 900 
14, 000 

4, 450 
5,450 
6, 850 
9,200 


7,370 

S, 050 
10, 100 
12, 400 
4,170 
5,350 
6,500 
8, 050 


6,900 
8,170 
9, 230 
11,000 
4,160 
5, 100 
5,900 
7,000 


Bending strengtli 

Crnsliing endwise — 

Mean (if both l>eiidiDgaud 
crushing strength 


1 33 
1 20 
1 15 
I 10 
( 33 
1 20 
15 

I lu 

( 33 
[ 10 


100 
118 
142 
181 
100 
132 
157 
184 
100 
125 
149 
182 


100 
116 
142 
182 
100 
122 
154 
206 
100 
119 
148 
194 


100 
117 
138 
168 
100 
128 
156 
206 
100 
122 
147 
187 


100 

118 
134 
160 
100 
122 
142 
168 
100 
120 
138 
164 


100 
117 
139 
173 
100 
126 
152 
191 
100 
122 
146 
182 



a33 per cent green, 20 per cent half dry, 15 per cent yard dry, 10 per cent room dry 




Variation of coinpiessioii slieii^(h uitli moisture. 



It will be obseiveil that the strength incrcnses by about 50 per cent in ordinary good yard seasoning, and that 
it can be increased by about oO pei" cent more by complete seasitning iu kiln or house. 

Large timbers leiiuiie several years before even the yard-season condition is attained, but L'-inch and lighter 
material is generally not used with more than 1.") per cent moisture. 



WKKHir .\Nl> MOI.STUUK. 

So far the weight of only the kiln-dry wood has been considered. In fresh as well as all yard and air-dried 
material there is contained a variable amount of water. The amount of water cont.ained in fresh wood of these 
pines forms more than half the weight of the fresh sapwood, and about one-fifth to oiie-fonith of the heartwood ; in 
yard-dry wood it falls to about 12 to 1.S per cent, while iu wood kept in well-ventilated and especially in heated 
rooms it is about 5 to 10 per cent, varying with size of piece, part of tree, species, temper.ature, and humidity of air. 
Heated to 150° F. ((15° C.) the wood loses all but about IJ to 2 per cent of its moisture, and if the temperature is 
raised to 175'^ F. there remains less than 1 per cent, the wood dried at 212'^ F. being assumed to be (though it is not 
really ) perfectly dry. Of course large pieces are in practice never left long enough exposed to become truly kiln-dry, 
though iu factories this state is often approached. 

As long as the water in the wood amounts to about .SO per cent or more of the dry weight of the wood there is 
no shrinkage' (the water coming from the cell lumen) and the density or specific gr.avity changes simply in direct 

'In ordinary lumber and all large size material the exterior parts commonly dry so much sooner than the bulk 
of the stick that checking often occurs, though the moisture per cent of the whole stick is still far above 30. 
H. Doc. 181 23 



354 



FORESTIiY 1N\'ESTIGATI0NS U. S. DEPARTMENT OF AGRICULTURE. 



I>riip()itii)ii to tlio liiss of Wiiti'i'. When tlio inoistiirr i>cr tout falls liilow about 30 the water coiiii'S from ttie itOl w:iil, 
:iu(l tUr loss of wutc^r ami weight is incoiiipaiiuul by a loss of volunio, so that both factors of the fraction 



Specilic gravity 



weight 
volume 



ari' adV^ctcd and the change in the specilic gravity no longer is siMii)ly proportional to the loss of water or weight. 
The loss of weight and volume, however, being uneciual and disproiiortionate, a marked redriction of the sjieeilic 
gravity takes place, amounting in these pines to about S to 10 per cent of the specific weight of the dry wood. 

SI11CI>'KA(1K. 

The behavior of the wood of the southern jjincs in shrinkage docs not difl'er materially. Generally the heavier 
wood .shrinks the most, and sapwood shrinks about oiu'-fonrth more than heartwood of the same specific weight. 
Verv lesinons pieces ("light wood") shrink much less than other wood. In keeping with these general facts, the 
slirinka'^e of the wood of the up])er logs is usually l."i to 20 ])er cent less than that of the butt pieces, and the 
shrinkage of the heavy heartwood of old trees is greater than that of the lighter peripheral ])arts of the same, w hile 
the shrinkage of the heavy wood of sa[)lings is greatirst of all. On the whole, the wood of these pines shrinks 
about 10 per cent in its volume, 3 to 4 per cent along the radins, and (! to 7 per ( ent along the tangent or along the 
yearly rings. 

After leaving the kiln the wood at ou<:c begins to absorb moisture and to swell. In an experiment with short 
pieces of loblolly and shortleaf, representing ordinary llooring or siding sizes, these regained more than half the 
water and underwent more than half the total swelling during the first 10 days after leaving the kiln (see tig. til). 
Even in this less than air-dry wood the changes in weight far excel the changes in volume (sum of radial and 
tan"ential swelling), and therefore the specilic gravity, even at this low per cent of moisture, was decreased by 
drying and increased by subse(iuent absorption of nu)isture. Innnersion and, still more readily, boiling, cause the 
wood to return to its original size, but temperatures even above the boiling point do not prevent the wood from 
"working," or shrinking, and swelling. 





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Fig. 94.— Loss of w-lter in kiln ilryinn .inil realisoriilion in .-lir, shrinkin;;, and swillini:. 

In lig. 04 are reproseuted the results of experiments on the rate of loss of water in the dry kiln and the reab- 
sor|ition of water in the air. The wood used Avas of loblolly and .shortleaf pine kept on a shelf in an ordinary room 
before and after kiln-drying. The measurements were made with caliper. 

EFFECT OF KILN-DRYING. 

Although kiln-drying has become quite universal, opinions arc still divided as to its eflects upon the strength 
of the material and other qualities. Many objections and claims as to physical and chemical changes produced by 
the treatment remain unsubstantiated. The method most widely used and most severely criticised is that of the 
"blower" kiln, where hot air (180- !•'.) is forced into the drying room by means of powerful fans. Besides the 



TIMBER PHYSICS SOUTHERN PINE. 



355 



miiny, in i);irf, imreasouable and contradictory claims about closing or opening of pores, chemical or physical 
influence on the sap and its contents, albumen, gum, re.sin, sugar, etc., substances whose very existence in many 
cases is problematical or doubtful, the general claims of increased checking and warping, "casehardening," 
"honeycombing,'' etc., as well as reduction of strength, are still prevalent even among the very manufacturers 
themselves. The manner and i)rogress of the kiln-drying may render this otherwise useful method of seasoning 
injurious. Rapid drying of the heavier hardwoods of complicated structure, especially in large sizes and fl-oin the 
green state, is apt to produce inordinate checking and thus weakening of the material. For Southern pine, however, 
it is entirely practicable to carry ou the process without any injury, as is evidenced by the following experiment, 
in which wood of Cuban pine in small dimensions (4 by 4) was seasoned in warm air (about 100- F. ) and parts of 
the same scantling were tlried at temjieratures varying from 150 at the entrance end to 190^ F. at the exit" 





Bending strength. 


Compression 

strength. 


Absolute. 


At elastic limit. 


Mean of material not kiln-drieu /reduced to 15 per 
cent of moisture) 


Lbg.penq.in. 
12, 200 
11,500 


Lbs. per sq. in. 
9,070 
9,180 


Lbs. per sq. in. 

8^550 


Average of kilu-dry materia] 





Well-constructed "blower kilns," where the hot air is blown in at one end and escapes at the other (this latter 
always the entrance end for the material), are giving satisfaction. The best kiln, however, .seems to be one in 
which ample piping in the kiln itself insures sufficiently high (up to 180^ F.), uniform temperature in all parts of 
the kiln, and where the circulation, promoted by a suction fan, is moderate and under perfect control. In such 
kilns even timbers of large size can be dried satisfactorily with a temperature not over 150^ F. 

Kl'FECT OF HKill-TE.MPERATURE AND HIGH-PKESSURE PROCESSES. 

For some time a process employing high temperature under high pressure (temperature over 300 F., pressure 
150 pounds) has been discussed and applied, claiming as a result of the treatment (1) increase in strength; (2) 
increase in durability; (3) absence of shrinkage. 

The result of a series of experiments in which a number of scantlings of lougleaf pine, one-half treated, the 
other untreated, is as follows: 





Beuding 
strength. 


Compression 
strength. 




Lbs. per sq. in. 
7,770 
12, 340 


Lbs. per sq. in. 
5,600 
7,400 







The same dift'erence in favor of tlie untreated material obtained in every single case. 

The chemical analyses performed on wood lying side by side along the same radius, being of the same annual 
rings and same position in tree, gave the following : 

Per cent of rosin aud phenols calculated to dry weight of wood. 





Tree No. 475. 


Tree No. 476. 


Average of both. 


Treated. 


tfntreated. 


Treated. 


Untreated. 


Treated. 


Untreated. 


Rosin: 


Per cent. 
1.21 
8.35 

0.061 
0.290 


Per cent. 
2.05 
10.58 

0.083 
0.180 


Per cent. 
1.22 
2.23 

0.045 
0.070 


Per cent. 
1.23 
1.93 

0. 083 
0.058 


Per cent. 
1.22 
5.29 

0.053 
0.180 


Per cent. 
1.64 
6.26 

0.083 
0.119 




Phenols: 







It appears that the protective rosin is rather decreased by the treatment, and the antiseptic phenols not 
increased in an adeciuate amount to l)e of value since it recjuires at least 20 times as much heavy oil in wood 
impregnation to be effective. It is, however, possible that the change of color due to the process may be accom- 
plished and be produced by the formation of empyreumatic bodies (allied to the humus substances) which may act 
as preservative against the attacks of fungi. 

The claim that the shrinkage of the wood is favorably inlluenced liy the process was not sustained by a .series 
of experiments with oak and i)ine, which showed that the treated wood absorbs water from air or in the tub, swells 
and shrinks in the same manner and to about the same extent as the untreated wood. 



EFFECT OF l.MMERSION ON THE STRENGTH OF WOOD. 



The notion fre(|uently expressed is that "soaking wood by floating, rafting, etc., reduces its tendency to decay 
and shrinkage, but injures its strength." The same was claimed for l)oiling or steaming preparatory to bendiu". 
The last position was disproved by Peter Barlow in the first iiuarter of this century. The followin"- figures (results 
of an experiment involving several hundred separate testa) disprove the former assertion. 



306 



FORESTRY INVESTIGATIONS IT. S. DEPARTMENT OF AGRICULTURE. 



The soaked wood was ke])t immersed six months, each piece having its check jiieces from tlie same scantling, 
which were not subject to the same process, but were tested — one green and one dry. All so;iked pieces were 
seasoned in dry kiln before testing. All values were reduced to 15 per cent moisture. 



Lobolly pine. 


BtindiDg 
strength. 


Coinpression 
strength. 




Lbs. per sq. in. 
10, B20 
10,570 


Lbs. per sq. in. 
6,780 
7,060 







EEFECT OF "jtOXINIi" OR ''BLEEDING." 

"Ulceding" pino trees for their resin — to which only the longleaf and Cuban pine are subjected — has generally 
been regarded as injurious to the timber. Both durability and strength, it was claimed, were impaired by this 
process, and in the sjiecifications of many architects and large consumers, such as railway companies, "bled" timber 
was excluded. Sime tlie utilization of resin is one of the leading industries of the South, and since tlie process 
affects several millions of dollars' worth of timber every year, a special investigation involving mechanical tests, 
physical and chemical analyses of the wood of bled and unbled trees from the same locality were carried out by this 
division. The results prove concusively (1) that bled timber is as strong as unbled if of the same weight; (2) that 
the weight and shrinkage of the wood is not affected by bleeding; (3) that bled trees contain practically neither 
more nor less resin than unbled trees, the loss of resin referring only to the sapwood, and, therefore, the durability 
is not affected by the bleeding process. 

The following talile shows the remarkable numerical similarity between the average results for three groups 
of trees, the higher values of the unbled material being readily explained by the difference in weight: 



LouijUaf pint'. 


Number (if 

teata. 


Specific 
weight of 
test pieces. 


Bending 

strength. 


Compreeaion 
strength. 




400 
390 
535 


0.74 
0.79 
0.76 


Lbs. per sq. in. 
12, 358 
12, 9til 
12, 586 


Lbs. per sq. in. 
7,166 

7,813 
7,575 









The amount of resin in tlie wood varies greatly, and trees growing side by side differ within very wide limits. 
Sapwood contains but little resin (1 to 4 per cent), even in those trees in which the licartwood contains abund.mce. 
In the hcartwood tlie resin forms I'roin 5 to 24 jier cent of tlie dry weight (of which about one-sixth is turpentine and 
can not be rcmoveil liy bleeding), so that its iiuantity remains unaffected by tlie jirocess. Hied timber, then, is as 
useful for all purposes as unbled. 

To give an idea how necessary it is that a large series of material be tested before making 
statements of the strength of wood of any species, we reprodnce one of the many tables contained 
in Bulletin 8, which at the same time exhibits the variation of strength throughout the tree and 
from tree to tree. 



TIMBER PHYSICS SOUTHERN PINE. 



357 



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358 



FORESTEY INVESTIGATIONS U. S. DEPARTMENT OP AGRICULTURE. 



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TIMBER PHYSICS REAMS AND COLUMNS. 



359 



SIZE OF TEST MATERIAL. 

The long- standing idea of engineers and other consumers to have wood tested more nearly in 
the sizes used in ordinary practice led to the adoption of test sizes, generally varying from 3 by 3 
inches to 4 by 4 inches. Besides this, special inquiries with different kinds of timber into the 
relation of large and small tests were instituted to ascertain the correctness of the general dogma 
which claimed that tests on small pieces could not be utilized, since such pieces for their very size 
gave higher values of strength. This investigation involved fall-size columns as well as beams, 
and was continued throughout the entire period of the timber-physics work. It led to a number of 
the most interesting and highly valuable results, as will appear from the following statements: 

Selected teats of columns and comjyreasion pieces from the same trees compared. 







Ratio 


Small pieces 


Large 










Number 
of tree. 


LeDgth. 


I 
d 


(average of 
whole tree). 


columns. 


Relative value. 


Deflec- 
tion. 


Failure. 






(a) 


(b) 


«j) 


w 








Feet. 




Pounds per 
sq. inch. 


Pmmdsper 
sq. inch. 






Inch. 




239 


12 


U 


6,700 


6,100 


100 


91 


0.7 


Shc-vrod. 


:;40 


]2 


14 


7,000 


0,900 


100 


99 


0.1 


Comitrcssioii. 


241 


12 


15 


(i, 900 


6,500 


100 


94 


0.7 


1)0. 


:i09 


12 


12 


6,800 


6,500 


100 


96 


0.4 


Do. 


312 


]2 


10 


6,100 


0,300 


100 


lO.T 


0.4 


Do. 



In thfso coliiiiius (nearly ono-tentb of all longloaf pine columns tested) the strength was so nearly the same as that 
of the short pieces that it appears .as if flexure had hut little to do with the failure, the small dift'erences hcing amply 
accounted lor hy a larger nuniher of defects in the columns. .Should this prove true in general for wooden columns 
as ordinarily designed, the problem would become simply a study of the influence of defects and of proper inspection. 

The nature of the failures would also point in this direction: 

Of 86 columns 32 failed noruially, i. e., in simple compression ; 22 were crushed near the end ; 14 failed at knots, 
and 19 by shearing, the rupture usually beginning at or near the ends; a small knot proved sufficient to cause a large 
column, 20 times as long as its dhameter, to fail at 14 inches from the end. 

The delleition in the average for all columns (12 to 20 feet long) w.as only .about 1 inch for the maximum 
load, when, to be sure, destruction h.ad progressed for some time; at the elastic limit the deflection w.as only about 
one-half as much. These results would seem to warrant the statement that for pine i olumns at least, in which the 
ratio of height to least diameter does not exceed 1 in 20, none of the accepted column formuhe .are applicable, the 
ii.ature of the failure being mostly in simple compression, and depending more on specilic defects than on the design 
of the column. 

STRENGTH OF LARGE BEAMS AND COLUMNS. 

Owing to the fact that muih wood testing has been done on small, select, and perfectly seasoned pieces, usually 
from butt logs, the values thus obtained seemed to dificr very markedly from the results on large tiii-bers usually 
very imperfectly seasoned, and it was claimed that tests on small sizes always furnished too high values, just as if 
the ditt'erences were due to sizes alone. 

While, to be sure, a small piece may be so selected that defects are excluded, the grain straight and in the 
most favorable position with regard to the load, the assumption of the difterence in strength of small jiieces from 
that of large-sized sticks has never lieen nuade good experimentally. 

Since it appears desirable to compare the results from Large beams and columns not only with the .aver.age 
d.ata obtained from the general test scries on small 4 by 4 m.ateri.al, but also with the average strength of small pieces 
cut from the s.ame beams and columns, a special inquiry into the h'gitimacy of sucli .a comp.ari.son w.as made. This 
study involved over 100 separate tests, .and proved the very important fact that uninjured parts of broken be.ams 
and columns do not sutler in the test. The large-sized beams varied from 4 bv 4 to 8 by 16 inches. 



Tests of large and small heams — Bcndiny 


streiujth. 






Sill.aU beams. 

general 
teat series. 


Largo bciras. 


Small be.ams 

cut from 
large beams. 


Total. 


Beams from 

wbich 

sm.all beams 

were cut. 


Number of tests involved 

Lon*^leaf 


1,986 


127 


57 


236 


Lbs. per sq. in. 
11, 300 
10,000 
9,300 


Lbs. per sq. in. 

11, 500 

10, 800 

9,200 


Lbs. per sq. in. 
9, 800 
10, 300 
8,700 


Lbs. per sq. in. 
10, 100 
10, OOO 
8,700 


Loblolly 


Shortleaf 





From the preceding table it would appear that Large timbers, when symmetrically cut (i. e., with the center of 
the log as center of the beam), develop as beams pr.ictically the s.ame strength as the aver.age of the small pieces that 
may be cut from them, and sometimes even higher values ; the explanation being that cut in this manner the extreme 
fibers which .are tested in a beam come to lie in th.at part of the tret^ which, as a rule, contains the strongest timber. 



3(50 



FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



Results (lisrordant frniii tlicsi' may ^»^ i-xplained by differences in the degree of seasoninfj of tbe onfer layers 
and alsd Iiy tlie fact that especially in the northern pineries timlx^rs are often c iit from the top logs, which are 
weaker and mure defective. 

'J'cxI of luriji' Hiid small culntniis — ( 'umpresshin strriiijth. 





Regular series 
from same trees 
as thecolumus. 


Columns (sim- 
ple compres- 
aioD). 


Small pieces 
cut from 
columns. 




949 


95 


97 




Lbi, per sq. in. 
6,600 
6,800 
5,900 
7,400 


Jjhg. per sq. in. 

.I, 300 
4,700 
4,100 
5,000 


Zihs. per tq. in. 

7,100 
6. 3U(I 
6,200 
8,700 


LobloUv 









The square columns were mostly 8 by 8 inches, some 10 by 10 inebes, a few of larger and also some of smaller dimen- 
sions. The ratio of length to width varied from 12 to 27, abont one-half being nuder and the other half over 18 to 1. The 
compression pieces of the regular series, and those cut from the broken columns, were in general .about 4 by 4 by 6 inches. 

It will appear from this statement of average results that columns develop only from 62 per cent (in Cuban 1 to 
78 per cent (longleaf) of the compression strength id ordinary short pieces. The explanation may be due to several 
reasons, natural and mechanical. In a column, unlike a beam, all the fibers are under great strain; hence all the 
defects, which .are by necessity found in every column, inlluenoe the results; the llexure of a column under strain is 
an element of weakness, to which the short compression pii'ce is nut subjeit. In addition tlie difliculty of determin- 
ing the average moisture condition of the large timl)er throughout the cross section an<l that of the small ])iece8 cut 
from them afterwards would render this method for colunnis less satisfactory; a larger number of tests will still be 
required to establish comparable average coiiditious in the two kinds of tests. It would, therefore, be un.safe to 
generalize too hastily from these average figures, at least as to the numerical difference, for there are remarkable 
individu.al exceptions. Not only do individual columns show ditVorences in strength 50 j)er cent and more lower 
than the compression pieces from the same log, but .sometimes they show practi<ally the same or even a higher value 
of strength, as will appear from the following selected cases, in which the data for the columns are placed in com- 
parison with those obtained on compression pieces from the same tree. 

AUDITIONAI. SkKIKS ON BEAMS AND Col.IMNS. 

A series more extended as regards beams, involving (58 large and 777 small beams, besides over 1,000 compression 
tests on the same material on which the beam tests were made, and tests on large columns, has fully confirmed the 
indications of the previous experiments. 

TK..STS ON COLUMNS. 

The colunnis were 12 by 12 inches and 8 by 12 inches in cross section, with a length of 132 to 108 inches. From 
these were cut, as near as i)osiible from the place of failure, two blocks 24 inches long, and these blocks were tested 
on the same large testing machine (described in Bulletin 6), so that inaccuracies of machinery do not enter into 
consideration. The results, tabulated as follows, prove conclusively the statement made upon the former more 
extensive series (see Circular 12), that wooden columns in which the diameter and length are to each other as 1 to 
18 or less behave like short blocks and fail in simple compression. The four columns of long-leaf pine exhibit 
practically the same strength as the short blocks — i. e., witbin 10 per cent — whicb, as has been shown above, is 
within the limits of maximum uniformity. 

SIreiigth of larye columns and short (Si-inch) hloclcs cut from Iheac cuhimns. 



Kind ol wood. 


Dimensions 

of colnmus 

(inches). 


Moisture 
of wood 
(per cent). 


Modulus o(" 
eh-isticity 
(pounds). 


Compre 

strength ii 
per sqnai 

Columns. 


ssion 
1 pounds 
e inch. 

•Short 
blocks. 




144 
132 


12 
12 


12 
12 


14.2 
12.9 


2.274,000 
1,740,000 


4,840 
4,840 


6.090 
5.660 


Do 




168 
168 
l.W 
158 


12 
12 
12 
12 


8 
8 
8 
8 


30.9 
32.3 
40.8 
29.7 


1, 628, 000 
1, 570, 000 
1, 764. 000 
1,776,000 


2,940 
3,170 
3, 030 
3,710 


2,950 
3,530 
3,310 
3,780 


Do 


Do 


Do 





BEAM TEST.S. 

The experiments, of which the following tables contain the principal results, were performed on beams 
generally 8 by 12 by 192 inches. After breaking the large beam 12 small beams were cut from the uninjured portion 
of tlie large beam' in snch a way that the entire cross section of the large piece was represented by two sets of 6 
small beams each. Besides these tests on small beams, the compression strength of part of the material was tested 
on small blocks, part of which was sawed and part split from ]>ortions of the large beam. (See diagram at head of 



' The legitimacy of using such material for such purpose has been fully established by a long series of experi- 
ments. (See Circular 12, Division of Forestry, p. 11.) 



TIMBER PHYSICS SIZE OP TEST MATERIAL. 



361 



table.) To avoid any complications due to ditterences or changes in moisture, the tests on large and small beams 
were performed the same day. 

Strength of larj/e beams and of umall beamx, and of compression pieces cut from them. 
[Tlanally 12 small beams cut. from the iiuinjured part of each large beam.] 











\/ 










BUTT 




6" 


S' 


/.Aff6£ 
B£A/I^ 


S' 


6" 




TOP 


6" 


6' 



























1\ 



SPI/TS/IIV£0 



3526 



2728 



/ 


2 


3 


4 


S 


6 



7 


8 


5 


/O 
/2 



SAWfu.SPi/r 



TV 



J 9 20 



2122 



S32't 



2930 



3/32 



Kiu.l of wood. 


Number 
of beam. 


Strength 
of large 
beams. 


Average 

strength 

of small 

beams. 


Moisture. 


Compression, 
endwise strength. 


iarge 
beams. 


Small 
beams. 


Sawed 
pieces. 


Split 
pieces. 






lihs. per 


Lbs. per 






Lbs.%ter 


Lbs. per 






so. in. 


sq. in. 


Per cent. 


Per cent. 


sq. in. 


sq. in. 


Oak 


2 


7,400 
5.880 


8,560 
8,660 


69.5 
70.3 


68.5 
69.0 


3,960 
4,340 


4,120 
4,700 






i 


6,570 


0. 220 


75.3 


75.:; 


3, 030 


3,190 




4 


8,640 


8.800 


66.6 


67.6 


4.0S0 


4,460 




,5 


8,150 


7,710 


64.8 


65.8 


3, 680 


3,750 




6 


7,450 


6,910 


63.0 


66.6 


3, 330 


3,330 




8 


6,870 


6,890 


67.4 


70.5 


3,470 


3,190 


Shortleaf pine. 


9 
10 


8,300 
7,440 


7,950 
7, 250 


48.1 
42.1 


57.7 
56.3 


4,030 
3,840 


4,160 
3,850 






11 


5,110 


6,760 


38.9 


.33.3 


3,870 


3, 630 




12 


7.360 


6,930 


35.2 


33.5 


3,890 


3,850 




13 


7,320 


7,300 


37.4 


40.6 


4,090 


3,800 


White pine 


14 


3,110 


3,560 


84.9 


83.6 


2,440 


2, .100 




15 


4.280 


4, 340 


43.8 


41.2 


2,710 


2,840 




16 


3,770 


4,590 


50.7 


50.5 


2,660 


2,760 




17 


3,460 


3, 590 


60.0 


48.6 


2,410 


2,570 




18 


3,990 


3,640 


42.8 


43.0 


2,800 


2,620 




19 


4,040 


4,400 


62.4 


60.4 


2, 760 


2,780 




2U 


4,410 


4,180 


53.6 


51.8 


2,680 


2,700 




21 


4,900 


4, 320 


50.1 


51.0 


3,010 


2,900 




22 


3,860 


4,320 


50.2 


60.8 


2, 500 


2,430 




23 


4,660 


4,890 


52.0 


58.2 


2,850 


2,880 




24 


3,960 


4,440 


76.3 


71.5 


2,520 


2,710 




25 


3,920 


4,410 


53.6 


60.5 


2,840 


2,730 


Shortleaf pine 


26 


4,560 
4,390 


6, 290 


31.2 


30.5 


3,660 


3,850 




27 


5,610 


33.9 


36.0 


2,830 


3,110 




28 


6,670 


6,830 


28.6 


28.9 


3, 540 


3,590 




29 


7.410 


7,630 


28.6 


29.0 


4,450 


4,250 




30 


6,600 


7,160 


28.3 


28.9 


4,200 


4,190 




31 


5.750 


6,000 


34.3 


35.5 


3,630 


3,530 




32 


6,210 


7,500 


26.4 


27.2 


3,940 


4,050 




33 


7,450 


8,390 


29.5 


30.1 


4,350 


4,220 




34 


7,000 


7,800 


28.4 


29.5 


4,070 


4,120 




35 


6,030 


«, 740 . 


28.8 


29.4 


3,810 


3,640 




36 


6, 520 


6,890 


31.6 


31.6 


4, 320 


4,370 




37 


7,030 


7,890 


29.2 


29.9 


4,380 


4,920 




38 


7,710 


8,510 


26.2 


25.4 


4,500 


4,610 




39 


8,090 


8, 210 


32.5 


31.9 


4, 550 


4,670 




40 


7,680 


7.980 


31.1 


32.3 


4, 290 


4,380 




41 


7,330 


8, 230 


31.7 


31.5 


4,680 


4,820 


I.ongleaf pine 


42 


7,290 


8.740 


30.9 


31.2 


4,950 


5,120 




43 


sisso 


9!720 


28.1 


28.9 


5,300 


5,440 




44 


8,040 


8,870 


26.3 


26.9 


4,730 


5,070 




45 


8,000 


H,850 


25.8 


25.4 


5.000 


5,050 




46 


7,620 


7,670 


32.6 


33.9 


4,730 


4,830 




47 


6,710 


7,610 


33.0 


33.4 


4,200 


4,520 




4R 


8,480 


8,300 


29.3 


29.3 


4, 870 


4,890 




49 


5,630 


0,250 


34.5 


33.7 


3,600 


3,630 


White pine. ......... 


50 


4. 900 
5,300 


5 020 


87 2 


75 7 


2,970 


3, 200 




51 


s! 210 


71.4 


69.6 


3,330 


3,240 




52 


4,810 


4,470 


77.2 


64.7 


■>, 940 


3,100 




53 


3,610 


3,610 


54.5 


58.2 


2,400 


2,550 




54 


4,440 


4,720 


97.6 


94.9 


2,710 


2,900 


Shortleaf pine 


55 


6,400 
6,690 


7,610 
6,880 


27.0 


27.1 


4,340 


4,500 




56 


28.4 


26.6 


4,050 


4,210 




57 


6,670 


6,990 


27.0 


26.4 


4,100 


4,340 




58 


7,310 


7,490 


28.5 


26.8 


4,100 


4,030 


White pine 


101 


5 070 


7,200 
6,890 


15.4 


16 2 


5,410 


5,720 




102 


6^340 


ii!o 


11.7 


4,920 


5,520 




103 


7,070 


8,750 


12.2 


10.5 


5,140 


5,760 




104 


4,900 


6,680 


12.1 


8.2 


4,360 


4,700 




105 


6,640 


6,890 


10.6 


11.2 


5,450 


5,310 




106 


6,180 


7,650 


11.6 


11.3 


5,190 


5,420 




107 


6,080 


6, 090 


11.5 


11.5 


4,810 


5,170 




108 


5, 510 


5, 810 


11.1 


10.7 


5,100 


4,710 




109 


6,930 


7,300 


11.4 


10.5 


5,330 


5,080 




110 


5, 930 


6,010 


12.1 


11.6 


4,600 


4,670 




111 


4,010 


.1, 040 


13.0 


13.0 


4,270 


4,390 



362 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGEICULTURE. 

OnSEHVATlONS AND DEDUCTIONS. 

(«) The dift'creiice between the values for the large beam and the average for the small beams is not at all 
constant, either in character or quantity; the large beam may be stronger (20 i>er cent of the cases) or practically 
as strong — i. e., within 10 per cent (57 per cent of the cases) — or it may be weaker, and vary often considerably from 
the average (23 per cent of the cases). 

Of 6% tests on small beams 2:i,5 furnished results smaller than that of the large beam. Again, out of 390 small 
beams fully 40 per cent were weaker that the largo beam, while of another series of 300 only 24 per C(mt gave lower 
values. 

(h) There are in every case some siuall beams which far excel in strength the large beam; even in such cases, 
where the average strength of the small beams is practically the same as that of the large beam, some small beams 
show values 25 to 30 per cent greater than the large beam. 

((') In only G per cent of the cases each of the small pieces gave a higher result than w.as obtained from the 
large beam, hut in these cases the latter was evidently defective. 

(d) In all beams the differences observed between the several small beams themselves are far greater than that 
between the average value of the small beams and the value of the large beam from which they are cut. 

From these observations, which are fully in accord witli the observations on the numerous tests of the large 
general series, it would ajipear that — 

(1) .Size alone can not account for the diflerences observed; .and, therefore, also that a small beam is not propor- 
tionately stronger because it is smaller, for it may be either stronger or weaker; but that if it is stronger, the cause 
of this lies in the fact that the larger beam contains weak as well as strong wood, besides other defects, which may 
or may not appear in the small stick. 

(2) Generally, but not always, a large timber gives values nearer the average, since it contains, naturally, a 
larger f|uantity as well as a greater variety of the wood of the tree; and, therefore, also — 

(3) Small beams, for the very reason of their smallness, containing, as they do, both a smaller (luautity and 
variety of the material, give results which vary more from the average than results from large beams, and. there- 
fore, can be utilized only if a sullicient number be tested; but it also appears that — 

(4) To obtain an average value, even a very moderate number of .smaller jiieces, if they fairly represent the 
wood of the entire stem, give fully as reliable data as values derived from a large beam. 

(5) Arcrai/e ralnen derived from a large xeririi of tests on small hut represenlaliee material may he ased in praetiee with 
perfeei safctij, and these arer((fii;s are not likehj to he modified hy tests on large material. 

It might be added that both the practicability and need of establishing a coefficient or ratio between results 
from tests on largo and small lie.ams or columns falls away. To deserve any conlidenco at all, only a large series of 
tests on either Large or small beams would s.atisfy the re(iuirement of establishing standard values, while a series of 
small pieces has the preference, not only on account of greater cheapness and convenience in establishing the values, 
but still more for the reason that only by the use of small, properly chosen material is it possible to obtain a 
sufficiently complete representation of the entire log. 

Before these results, part of wbicli were published by installments, had all been eomputed 
and arranged, the results of the work made it possible to publish, for the first time in the English 
language, a brief exposition of tiie teehniral properties of wood in general, which appeared as 
Bulletin 10 of the Division. This little booklet was copied verbatim several times by different tech- 
nical journals of this country, was embodied in toto in one of the best works on the materials of 
engineering, and was even translated into French by one of the foremost i>ublishers of France, 
besides being nsed itself as a text-book by several of our largest colleges. In addition to the 
discussions of the several technical properties of wood, tliis booklet contains the first attempt in 
the Engli.sh language at a key by which our common woods may be safely recognized from their 
structure alone. The key and some of the tables in this bulletin have been reproduced in an 
earlier jjart of this report. By this time, when the work was interrupted by superior orders, there 
were brought together the strength values for the wood of 32 species, of which 2(J were represented 
by more than 200 tests each (the longleaf pine by over 0,000), 17 of them by over 400 tests per 
species, and seven by over 1,000 tests. These results were published in full in (circular No. 1.5 of 
the Division, from which the following extract is here repeated: 

Summary or Mechanical Tests on TniUTY-TWo Si-ecies of American Woods. 

GENERAL REMARKS. 

The chief points of superiority of the data obtained in these investigations lie in, (1) Correct identification of 
the material, it being collected by a competent botanist iu the woods; (2) selection of representative trees with 
record of age, development, place and soil where grown, etc.; (3) determination of moisture conditions and specific 
gravity and record of position in th(^ tree of the test pieces; (4) large number of trees and of test pieces from each 
tree; (5) emphiynient of large .and small-sized test material from the same trees; (0) uniformity of method for an 
unusally large number of tests. 

The entire woiU of the mecdianic.al test scries, carried »n tlumigh nearly six years intermittently as funds 



TIMBER PHYSICS — STRENGTH OF SPECIES. 



363 



wero available, comprises so far 32 species with 308 test trees, furnishing over 6,000 test pieces, supplying material 
for 45,336 tests in all, of which 16,767 were moisture and specific gravity determinations on the test material. 

In addition to the material formechanical tests, about 20,000 pieces have been collected from 780 trees (including 
the 308 trees used in mechanical tests) lor physical examination to determine structure, character of growth, specific 
gravity of f^reeu and dry wood, shrinkage, moisture conditions, and otlier properties and behavior. 

In addition to the regular series of tests, the results ol' which .arc recorded in the subjoined tables, special 
series, to determine certain (|uestions were planned and carried out in part or to finish, .adding 4,325 tests to the 
above number. 

rtncoiiiil of test material. 



No. 


Name ol* species. 


Num- 
ber of 

trees. 


Number 

of me- 

clianicll 

tests. 


Average 
specific 
gravity 
ol'iirv 
woimI. 


Localities and number of trees from each. 


1 




68 

12 

22 

32 

17 

8 

4 

20 

4 


6,478 

2,113 

1,831 

3,335 

540 

412 

696 

3,396 

354 

225 

1,009 

911 

256 

935 

299 

479 

222 

132 

649 

1,035 

794 

300 

197 

100 

294 

172 

84 

91 

201 

476 

45 

508 


0.61 

.63 
.51 
.53 
.38 
.50 
.44 
.46 
.37 
.51 
.80 
.74 
.80 
.74 
.73 
.73 
.72 
.73 
.72 
.73 
.81 
.85 
.73 
.77 
.78 
.78 
.89 
.54 
.74 
.62 
.62 
.59 


Alabama, coast plain (22) a; nplands(6); bill district (6) ; Georgia, undulat- 
ing upl.iuds (G) : Soutli Carolina, coast plain (7): Mississippi, low coast 
plain (2); Louisiana, low coast plain, gravelly soil i7); sandy loam (6); 
Texas, low coast plain (6). 

Alabama, coast plain (6) ; Georgia, uplands (1) ; Soutb Carolina, coast (5). 

Alabam.a, uplands (4) ; Missouri, low hilly uplands (6); Arkans.as, low billy 

uplands (6); 'I'exas, ujdaiids (0). 
Alabama, mountainous ].l;tii';in ih) ; low coast plain (6) ; Ark.ansas, level flood 

plain (5) ; Geoigi.i, lovil mast plain (6) : Soutb Carolina, low coast plain (7). 
Wisconsin, cl.iy uplands (5); sandy soils (4) ; sandy loam (5) ; Michigan, level 

drift lands (3). 
"Wisconsin, drift (5) ; Michigan (3). 

Ababama, low coast plain. 

South Carolina, pine barren (6) ; river bottom (4) ; Louisiana, coast plain, 

border of lake (4) ; Mississippi, Yazoo l>ottom (3) ; upland (3). 
Mississippi, low plain. 

(From lumlier yard.) 

Alab.ania, ridges of Tennessee V.alley (5) ; Mississippi, low plain (7). 

Mississippi, low plain (7) ; Arkansas, Mi8sissij>pi bottoms (3). 

Alabama, Tennessee Valley (5) : Arkansas, Mississippi bottom (3). 

Alilbania, Tennessee Valley (4) ; Arkansas, Mississippi l)ottonis (3) ; Missis- 
sippi, low ]dain (4). 
Alabama, Tennessee Valley (5) ; Arkan.sas, Mississippi bottom (2). ft / 

Arkansas, Mississippi bottom. 

Alabama, Tennessee Valley (5) . 

Mississippi, low plain (4). 

A]ab.ama, Tennessee Valley (5); Arkangas, Mississiiijii bottom (3); Missis- 
sippi, low plain (4). 

Alabama, Tennessee Valley (5) : Arkansas, Mississipiii bottom (3) ; Missis- 
sippi, low plain (3). 

Mississippi, alluvial plain (3); limestone (3). 

Mississippi, low plain. 
Do 


'> 


{PiDiis paluetris.) 


1 


(Pinna hetorophylla.) 


4 


(Pinus ecliinata.) 


R 


(Finns tieda.) 


6 

7 


(Pinus atrobua.) 

Red pine 

(Pinu.s resinosa.) 


H 


(Pinus glabra.) 


9 
10 


(Taxodium distiehum.) 
White cedar 

(CIiiini.TTyparis tbyoidea.) 


11 


(r.4.inb>tsuga taxilolia.) 
Wbity uiik . 


12 
10 
8 
11 

3 
5 
4 
12 
11 
6 
4 
o 

4 
3 

3 

3 
3 

1 
7 


T> 


(Qnercus alba.) 


v^ 


(Quercus lyrata.) 


u 
IS 


(CJuercus minor.) 

Cow oak 

(Quercus niichauxii.) 


1f» 


(Quercus rubra.) 


17 


(Ouercua texana.) 


T* 


(Quercua velutina.) 




(Quercus nigra.) 


?n 


(Quercus pbcUos.) 


^1 


(Quercus digitata.) 


00 


(Hicoria ovata.) 


0^ 


(Hicoria alba.) 


?4 


(Hicoria aquatica.) 




Or^ 


(Hicoria minima.) 




26 


(Hicoria niyristicjtfomiis.) 

Pecan hickory • . 

(Hicoria pecan.) 


Do. 
Do 


''fi 


(Hicoria glabra.) 


Mississippi, bottom. 


oq 


(Ulmus americana,.) 


:^o 


(Ulmus crassifolia.) 
White ash 


Misaiasippi. bottom. 
Do 


31 


(fraxinus americana.) 
Green ash 


s*> 


(Fraxinus lanceolata.) 
Sweet *'uni . 


Arkanaaa, bottom (3) ; Mississippi, low plain (4). 




(Liiiuidambar styraciflua.) 



a Sixteen of these were bled trees to study the etTects of boxing. 

& These two should probably be classed as Soutliern red oak. Thoy were collected before the distinction was finally decided npon. 

Note.— The values for specific gravity here given refer to "dry'' wood of test iiialerial— i. e., wood containing variable amounts of 
moisture below 15 per cent; the moisture Btlect has therefore not been t.aken int" :!■ fiiuiit, but more careful experiments indicate thtit its 
nfluence on specific gravity at such low per cent is so small that it may be neglected lor practical purposes. 

As will be observed, some species, notably the Southern pines, have been more fully investigated, and the results 
on these (wliich have been published more in detail in Circular No. 12) may be taken as authoritative. With those 
species of which only a small number of trees have been tested this can be claimed only within limits and in 
proportion to the number of tests. 



364 



FORESTRY INVESTIGATIONS V. S. DEPARTMENT OF AGRICULTURE. 



The great variation iu strength which is noticeable iu timber of the same species makes it necessary to accept 
with cantiou the result of a limited number of tests as reiiresintiuf; the average for the species, for it may have 
liappcnid that only all superior or all inferior material has been used in the tests. Hence we would not be entitled 
to conclude, for instance, that pignut hickory Is 14 per I'ent stronger than shagbark, as it would a)ipear iu the t.able, 
for the 30 test jiieces of the former uniy easily have been superior material. Only a detailed examination of the test 
pieces or a fuller scries of tests would enlighten us as to the comparative valne of the results. 

Till- following data, therefore, are not to ho considered as iu any sense hual values for the species, except where 
the number of trees and tests is very largo; 

J!e8iills of lr$l>i hi compresxinii endwise. 
[Pounds per square iuch.] 



Species. 



Reduced to 1:'> per cent moisture. 

Longleaf pine 

Cubau piue 

Shortleaf pine 

liOltlnlly piue 

Reduced to U per cent moisture. 

Wliite pine 

Ked piue 

Sprnee piue 

Billd evpress 

Wliile red.ar 

l)ouy;las spruce a 

White oiiU 

( K'ert^up oali 

Post ojik 

Cow oak 

Ited o:ik 

'rcxan oak 

Veliow oak 

Water oak 

Willow o.ak 

Spanish oak 

Stiagbark laickory 

Mockeruut liickoVy 

Water hickory 

iJittcriuit hickory 

Nut (I leg liickory 

Pecan liickory 

Pignut liickory 

AThiteelm '. 

Cedar elui 

White ash 

Greeu ash 

Sweet gxim 



Number 
of tests. 



1,S30 
410 
330 
660 



ISO 

100 

170 

655 

87 

41 

218 

•JIU 

49 

250 

57 

117 

40 

31 

153 

251 

137 

75 

14 

25 

72 

37 

30 

18 

44 

87 

10 

118 



Highest 
single test. 



Lowest 
single test. 



11.900 
10, 600 
8,500 
11,200 



8, 500 
8,211" 

10,(100 
», 900 
6,200 
8, tlllO 

12,500 ! 
9,100 
8, 200 

11,500 
9,700 I 

11,300 ! 

8, 600 

9, 200 
11.000 
10,600 
13,700 
12, 200 
10,000 
11,500 
12, 300 
10, 500 
13,000 

8, 800 
10, '600 

9, 600 
fl, 800 
8,900 



3, 400 

2, 800 

4, 500 

3, 900 



3, 200 
4,3011 

4, 400 

2, 900 
3,200 

4, 100 
5, 100 

3, 700 

5, 000 
4,600 
5. 400 
5, 800 

5, 500 

6, 200 

4, 200 
3, 700 

5, 800 
fi. 200 
0,700 

7, 300 

6, 400 
5, 8!I0 
8,700 
4,900 
6,200 

5, 000 

6, 600 
4,600 



Average 
highest 10 
per cent 
of tests. 



8,600 
9, 500 
7,600 
8,700 



6, 800 
8, 100 
8,8110 
8, 500 
6, 000 
8,100 
11,300 

8, 600 
8, 100 

9, 8U0 
9, 20O 
9, 800 
8,300 
9, 000 

8, 700 
' 9, .500 

10, 900 
11,000 

9, 000 
11,200 
11,000 
10, 400 
12,700 

8, 800 
10, 100 
8, 700 
9,800 
8,500 



Average 

lowest 10 Average 
pdr cent I of all tests. 
of tests. 



5, 700 
6, 500 
4, 800 
6,400 



4, 000 

4, 900 

5, Olio 
4, 200 
4,4110 

4, 20(1 

6, 3110 
0, 000 
6, 000 

5, 000 

5, 500 

6, 900 

5, 800 

6, 300 
5, ,500 
5, 100 

7, 500 

8, 000 
7,000 
7,800 
7,100 

7, 300 

8, 900 

5, 000 
0, 500 
5,700 

6, 000 
5, 000 



6,900 
7,900 
5, 90P 
6,500 



6,400 

6, 700 

7, 300 

6, 000 
5, 200 
5, 700 

8, ,500 

7, 300 
7, 100 
7, 400 
7, 200 
8, 100 
7, 300 
7, 800 
7, 200 

7, 700 

9, .500 
10, 100 

8.400 
!l. tioo 

8, 800 

9, 100 
10, tlOO 

0, .500 
8, 000 
7. 200 
8,000 
7, 100 



Proportion 

of tests 
within 10 
per cent of 

average. 



Per cent. 
53 
61 
47 
49 



Proportion 
of tests 
within 25 

per cent of 
average. 



Per cent. 



90 
93 
90 
84 



93 
96 
95 
74 
99 
65 
81 
95 

100 
89 
94 
98 

100 

100 
88 
94 
97 
99 

100 

100 
97 
95 

100 
88 
95 
96 

100 
97 



a Aotual tests on "dry" material not reduced for moisture. 

The v.ari.ation iu strength in wood of the virgin forest, as will be seen from the tables, is in some species so 
great that by projicr inspection and selection values ditt'eriug by 2v> to 50 per cent may be obtained from different 
parts of the same tree, and values differing 100 to 2O0 jier cent within the same species. These diflerences have all 
their definite reeognizaldl^ causes, to find and formulate which is the final aim of these investigations. 

The tests are intentionally not made on selected material (excejit to discard absolutely defective pieces), but on 
material as it comes from the trees, so as to arrive at an average statement for the species, when a sufficient number 
of trees has been tested. How urgent is the need for data of inspection as above indicated will appear from the 
wide range of results recorded. 

To enable any engineer to use the d.ata here given with duo caution and .iudgment, not only the r.anges of values 
and the average of all values obtained, but .also the proportion of tests which came near the average values, have 
been stated, as well as the aver.age results of the highest and lowest values of 10 per cent of the tests. With this 
informatiou and a statement of the actual number of tests involved, the comparative merit of the stated values can 
be Judged. With a large number of tests, to be sure, it is more likely that an average value of the sjiceies has been 
found. The actual test results have been rounded off to even hundreds in the fables. 



FACTOR.S OF SAFETY. 

With such lowest standard values, also lowest factors of safety could be employed. As to factors of safety, it 
may be proper to st.ate that the final aims of the present investigations m;iy be summed up in one proposition, 
namely, to establish rational factors of safety. It will be admitted by all engineers that the factors of safety as used 
at ]irescut can hardly be claimed to be more than guesswork. There is not an eugineer who eould give .account as 
to the basis upon which numeiically the factors of safety for wood have been established as "8 for steady stress; 
10 for varying stress; 1,5 for shocks" (see Merriman's Testbook on the Mech'inics of Materials); or as 1 to .5 for 
"dead" load and ."> to 111 for "live" load (see Rankiue's Handbook of Civil Engineering). 



TIMBER PHYSIC8 FACTOR OP SAFETY. 



365 



'J'lie <liiPction8 for usiuj; these indeteriiiinatc factors of safety given in the text-books would imply that the 
student or engineer is, after all, to rely on his judgment as to the moditieation of the factor, i. e., he is to add to this 
general guess his own particular guess. The factor of safety is in the main an expression of ignorance or lack of 
confidence in the rcli.ability of values of strength, upon which the designing proceeds, together with an absence of 
data upon which to inspect the material. With a linger number of well-conducted tests, coupled with a knowledge 
of the quantitative as well as qualitative iutluence.s of variou.s factors upon strength, and with definite data of 
inspection which allow ready sorting of material, the factor of safety, as far as it denotes the residuum of ignorance 
which may be assumed to remain, as to the character and behavior of the material, may be reduced to a niininium, 
restricting itself mainly to the consideration of the indeterminable variation in the actual and legitimate application 
of load. 

Jitatdts of It'sta in eumprcssion vnttwise on (jrtcii wood (ahorr JO per cent moistiirt'j not reduced). 

[I'oumls per stxiiaru inch.] 



No. 



.Species. 



Lonple.af pine 

Cuban pine 

Shortleaf pine 

Loblolly pine 

.Spruce pine , 

Bald cypress 

Ay hite cedar 

White oak 

Overcup oak 

f'ow oak 

Tex.an oak 

Willow oak 

Spanish oak 

Shagbark hickory... 
Mockernvit hickory 

Water hickory 

Nntmeg hickory . . . 

Pecan hickory. 

Pipmit hickory 

Sweet gum 



Number 
of tests. 



69 
71 
280 
34 
25 
45 
68 
39 
49 

.';2 

22 
18 
4 
26 
4 
5 
6 



Highest 
single 
test. 



7,300 
6,100 

4, 001) 
5,500 
4,700 
8,200 
3,400 
7, 000 
4,900 
4,900 
6,000 

5, 600 
6,100 
6, 900 
7,200 
5, 60U 
5. 500 
3, 800. 
6,200 
3,600 



Lowest 
single 
teat. 



2,800 
3,'500 
3,000 
2, 600 

2, 8011 
1,800 
2,300 

3, 200 

2, 800 
2,300 
3, 100 
2,300 
2, 5110 
3,500 
4,500 
4,700 
3,700 

3, 300 
4,700 
3,000 



Average 
of all 
tests. 



4, 300 
4, 800 
3, 300 
4,100 
3, 900 
4,200 
2,900 
6, 300 
3, 800 
3,800 

5, 200 
3,800 
3, 900 
5,700 

6, 100 
5, 200 
4,600 
3,600 
5, 400 
3, 300 



While the values given in these tables may claim to contain more elements of reliability than most of those 
published hitherto, nmch more work will have to be done before the above-stated aim will be satisfied. 

In explanation of the table recording tests in bending at relative elastic limits it should be stated Ihat since 
an elastic limit in the sense in which the term is used for metals, namely, as a point at which distortion becomes 
disproportionate to load and a permanent injury ami set results, can not be readily dcti'rmined foi- wood. Prof. ,1. B. 
Johnson has proposed to utilize a iioiut where the rate of distortion becomes 50 per cent greater for the amount of 
load than it was for the initial load, which point can bo tolerably accurately determined (see Bull. 8, p. !)). This 
point he has called the "relative elastic limit." The assumjition is that such a jioint would be near the limit to 
which tlie nuiterial can be strained without permanent injury, and the strength values obtained at that point woul<l 
serve for indications of safe loads. 

The practical utility of determining this ]ioint and the strength values relating to it remains, however, still 
open for discussion. A comparison of the values olitained for the strength at rupture and at relative elastic limit 
shows a ]iarallclism which would make it ([uestiouable whether much is gained by the use of that point, which in 
reality lies bej'ond tlie limit where practical injury has liegnn, as indicated by the increased distortion. 

We would be inclined to consider that point more serviceaVile where the curve begins to dcniate from the straight 
line, at which point we may .assume no permanent injury has as yet been experienced. This point we may call 
provisionally the "s.afe limit." 

Objection has been made to utilizing tills point because it can not be located with as much nicety and mathe- 
matical precision as the point of "relative elastic limit." But even this point is only approximately definable; and 
since no strength values can claim to lie more than approximately correct, it would suffice to determine the safe- 
limit point and the correspondent strength values also only approximately. This point has the advantage that it 
lies on the safe side. 

Special series of tests to investigate the legitimacy of the use of any of these limits for practical purposes 
w-ere designed, but have as yet not been taken up, and hence the values in the table on p. 367 are given (mly as 
suggestions tbr what they are worth. 



360 



FOKESTRY INVESTIGATIONS U. S. DEPARTMENT Ol' AGRICULTURE. 



lieaiiUs of Cecils in bendimj, at rupture. 
[Pouuds per square inch.] 



No. 


Spccius. 


Nnniber 
of tests. 


Highest 
single test. 


Lowest 
single test. 


Average 

highest 10 

per rent of 

tests. 


Average 

lowest 10 

per cent of 

tests. 


Average of 
all tests. 


Proportion 

of tests 

within 10 

per cent of 

average. 


Prnporliou 

of tests 

within 25 

per cent of 

average. 


1 
2 


Ueduced to 15 2)er cent moitture. 


1,160 
300 
330 
650 

120 

95 

170 

655 

87 

il 

218 

216 

49 

250 

57 

117 

40 

31 

153 

257 

187 

75 

14 

25 

72 

37 

30 

18 

44 

87 

10 

118 


17, 800 
17, 000 
15, 300 

14, 800 

11,100 
12, 1100 
16,300 
14,800 
9, 100 
13, 000 
20, 30O 
19, 600 
16, 400 
23, 000 
1 6. ,500 
19, 500 

15, 000 
10, 000 

16, 000 

17, 300 
23, 300 
20, 700 

18, OOO 

19, 500 
16,600 
18, 300 
2:i, 000 

14, 000 
19, 200 

15, 000 

16, 000 
14, 400 


3,300 

2, 900 
6, 000 
3, 900 

4,600 

3, 100 

3, 100 

2, 300 
3,500 
3,800 
5, 700 

4, 900 
.5, 100 

3, 300 
5,700 
8,200 
5,100 

5, 800 
3,200 
5, 000 
.■), 700 

5, 300 

6, 300 

7, 000 
0, 700 
.5, 600 

11,100 
7,300 
6, 6(10 
5, 000 
5,100 
5,100 


14,200 
14,600 

12, 400 

13, 100 

10, 100 

12, 300 

13, 600 
11,700 

8,400 
12, 000 
18,500 

14, 900 
15, 300 

12. 500 
15,400 

16, 900 
14,600 

15, 700 

13, 800 
15, 600 
20, 300 
19, 700 
17.300 
19, 300 

15, 600 
18, 100 
24, 300 

13, 600 

17, 300 

14, 200 

16, 000 
12, 700 


8, 8110 
8, 800 
7,000 
8,100 

5,000 
4,900 

5, 800 
5, 000 
4,000 
4, 100 
7,600 

6, 300 
7,400 
6,500 
9,100 

10,000 
5, 700 
7,200 
5,400 
6,900 
9,400 

7, 900 
,1, 400 

8, 700 
8, 100 

10, 300 
11,500 

7, 300 

8, 500 
6, 300 
5, 100 
6,000 


10,900 
11,900 
9,200 
10, 100 

7,900 
9, 100 
10,000 
7, 900 

6, 300 

7, 900 
13, 100 
11,300 

12, 300 
11,500 
11,400 

13, 100 
10,800 
12, 400 
10, 400 
12, 000 
16,000 
15,200 
12, 500 
1,5,000 

12, .500 
16, 300 
18, 700 
10, 300 

13, 500 
10, 800 
11,600 

9,500 


Pi-r cent. 
41 
46 
40 
44 

43 

28 
43 
25 
32 
22 
39 
47 
47 
32 
46 
64 
28 
40 
33 
40 
46 
45 
21 
28 
40 
38 
43 
44 
50 
37 
20 
39 


I'cr cent. 
84 




83 




79 


4 




84 


Reduced to 12 per cent moisture. 


81 


e 

7 
8 
9 
10 
11 
12 
13 




60 




81 




69 


Whito cedar 


78 
58 




75 


Oven up uak 


81 
92 


14 
15 
16 




68 


v„rf n-ilf 


84 




86 


17 
18 
19 
20 
21 
22 

24 




65 




76 




70 




72 


Shajxbark hickory 

Moekernut liiokory 


84 
78 
64 




60 




88 


26 
27 


reran hiekory 


95 

77 




72 


•J9 
31 




86 


White ash 


77 




60 




79 







a Actual tests on "dry" material not reduced lor moisture. 



KEI.ATIONS Ol- WEIIillT ANIi 8TRKNGTH. 

Th;it within the same species the strength of wood varied with the dry weight (spoeilic gravity), i. e., that 
the heavier stick is the stronger, has Ijeeu known for some time. That this law of variation held good not only for 
a given sjiecies, but irrespective of species for the four principal pines of our Southern States was indicated in 
Circular 12 of this Division. Tliis fact liecomes the more important in practical application, as the wood of these 
species of pines so far can not be distinguished at all by its anatomical structure and only with difficulty and 
uncertainty by other appearances, while in the lumber market substitution is not iufrc(iu(tnt. It will therefore be 
best with these pines, where strength alone is desired, to inspect the material by weight (specific), other things 
being eiiual, disregarding species determination. 

While this result of the exhaustive series of tests reasonaldy well demonstrated for these jiines may be 
considered of great practical value, we can now extend the application of the law of relation between weight and 
strength a step farther, .and state as an indication of our tests that probiibly in woods of uniform structure strength 
increases with specific weight, independently of species and genus distinction, i. e., other things being equal, the 
heavier wood is the stronger. We are at present inclined to state this important result with caution, only as a 
probability or indication, until either the test material and tests can be nioio closely scanned, or more carefully 
planned .and minutely executed series of detail tests can be carried on to confirm the truth of what the wholesale 
tests seem t<> have developed. 

In the following two diagrams the average strength of the difi'erent species in compression endwise and 
bending, as found in the preceding tables, has been plotted with reference to the dry weight as given in preceding 
table. 

Considering that these tests and weight determinations (especially the latter) wore not carried on with thiit 
finesse which would be reiiuired for a scientific demonstration of a natural law, that other inlliienees, as crossgrain, 
unknown defects, and moisture conditions may cloud the results, and that in the averaging of results undue consid- 
er.ation may have been given to weaker or stronger, heavier or lighter, material, the rcl.ixation is exhibited even by 
this wholesale method with a remarkable degree of uniformity bordering on demonstration. 

An exception is apparent in tlie oaks in thai they do not exhibit this rel.ation of weight and strength with 
reference to other species, and also with less definiteness among the various species of oak in themselves. The 
structure of oak wood being exceedingly complicated and essentially diU'eicnt from that of tlie wood ..f all other 
species under consideration, it may reasonably be expected that it will not range itself with these. 



TIMBER PHYSICS STRENGTH AND WEIGHT. 



367 



Reaidls of testa in hcndiny, at relatiw elastic limit. 
[Pounds per square inch.] 



No 



Species. 



Reduced to 15 per cent moisture. 

Longleaf pino 

Ouban pine 

Sbortleaf pine 

Loblolly pine 

Jieduced to 12 per cent moisture. 

White pine 

Ited pine 

Spruce pine 

li;ild cypress 

White cedar 

l>ou;L;las sjirucetr 

White oak 

Overcu}! oak 

Post oak 

Cow oak 

Ked oak 

Texan oak 

Yellow oak 

Water oak 

Willow oak 

Spanish oak 

Sbagbark hickory 

Mi>ckernut hickory 

Water hickory 

Bitternut hickory 

^Nutniej; hickory". 

Pecan hickory 

Pignut hickory 

White elm 

Cedar elm 

White ash . ^ 

Green ash 

Sweet gum , 



Number 
of tests. 



1,100 
a9o 

■SM 
650 



i:iO 

9.5 
170 
055 

87 

41 
•JIS 
•_'!« 

4!) 
•J5li 

57 
117 

40 

:n 

153 

257 

187 

75 

14 

25 

72 

37 

30 

18 

44 

87 

10 

118 



Highest 
single 
test. 



13, 500 
12, '.too 
11,900 
12, 700 



10, 000 
11,300 
13, 700 
12, 000 

8,200 
13,700 

15, 700 
11,000 
lO.liOO 

14, 2U0 
14,500 

12, UOO 

11, 800 
11, 800 

13, 100 

13, 500 

16, 100 

15, 400 
11,900 

14, 300 
12, 200 
15,1100 
17,500 

9,700 
10, 700 
11, 500 
13, 200 
11,000 



Lowest 
aiugle 
test. 



2, 400 
2, 200 
2,900 
3,100 



4,100 
3, 100 
3,000 
2,200 
3.400 
2,800 
4,400 
4, 000 
5,100 
3.400 
5, 100 
5,900 
4, 900 
4, 500 
2, 700 
5,100 
5,400 
4,300 
4,100 
7,500 

4, 200 
5,800 
7,400 

5, 300 
4, 700 
3,600 
3,200 
3,500 



Average 
of high- 
est 10 per 
cent of 
tests. 



11,100 
11,500 
9,700 
10, 800 



8.200 
10, 300 
11.200 
9, 900 
7, 390 
9, 600 
14, 100 
9,500 
9,600 
11, 600 

13, COO 
11, 400 
11,100 
11, 400 
10, 000 
11,600 
14, 200 

14, 600 
11,800 
14, 000 
11,200 
14,400 
16 400 

9, 600 
10, 100 
10, 400 
13, 200 
10, 100 



Average 

of lowest 

10 per 

c.ent of 

tests. 



5,400 
5,600 
4, 800 
5,400 



4, 500 
4,500 
5, 000 

4, 200 
4,000 
3, 400 
0, 100 
5,400 
6,000 

5, 000 
5,600 
7,800 
5,100 
5, 500 
4, 300 

6, 600 
7,700 
7,800 
4, 800 
7,600 
6,400 
7,900 
8, 300 
5, 400 
5,800 
5,200 
3,200 
5,100 



Average 
of all 
tests. 



8, 500 
9,500 
7,200 
8,200 



6,400 
7,700 
8.400 
6, BOO 
5,800 

6, 400 
9,000 

7, 500 
8,400 
7, 600 
9, 200 
9,400 
8,100 
8,800 
7,400 
8,600 

11,200 
11, 700 
9, 800 
11,100 
9, 300 
11,. 500 
12,600 
7, 300 
8,000 
7,900 
8,900 
7,800 



Proportion 
of tests 

within 10 
per cent of 

average. 



Proportion 
of testa 

within 25 
per cent of 

average. 



Per cent. 
43 
42 
48 
46 



Tcr cent. 

81 
83 
81 
85 



Alodulua of 
elasticity 
(average of 
all tests) . 



1, 890, 000 

2, 300, 000 
I, 600, 000 
1, 950, 000 



300, 000 
620, 000 
640, 000 
290, 000 
910,000 
6K0, 000 
090, 000 
620, 000 
030, 000 
610,000 
970, 000 
860, 000 
740, 000 
000, 000 
750, 000 
930, 000 
390, 000 
320,000 
080, 000 
280, 000 
940, 000 
530, 900 
730, 000 
540, 000 
700, 000 
640, 000 
050, 000 
TOO, 000 



a Actual tests on " dry " material not reduced for moisture. 



/siipao 



//,000 



i moo 



9000 



'i. 8000 



17000 



6000 



SOOO 




Weight pur ctibii; foot in pounds. 



Fig. 95.— Eelation of strength in compression endwise to weight of material. The ligurc at each point indicates the species 

thereby represented. 



368 



FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



moo 



/ROOO 



/7000 



moo 



/sooo 



uooo 



I /3,000 



/2000 



f //ooo 



/oooo 



9000 



8000 



7000 



^000 




AVeijiht per cubic foot in i>oimds 



Fui. 96.— Kelaliou of weight to bending strength at rupture. The figure at each point iutUcatea the epeciea thereby 

represented. 



TIMBER PHYSICS UNIFORMITY OP STRENGTH. 



369 



In addition, the difficulty of seasoning oak without defects or even securing perfect material may have influenced 
the results of tests so as to cloud the relationship with the genus. 

If further close study, su|)pli-mented by additional series of tests carefully devised to investigate this relation- 
ship, should uphold the troth of it, this result may ho set down as the most important practical oue that could he 
reached by these tests, for it would at once give into the hands of the wood consumer a means of determining the 
relative value of his material as to strength and all allied properties by a simple process of weighing the dry material ; 
of course with due regard to the other disturbing factors like crossgrain, defects, coarseness of grain, etc. 

Ri'snits of (<•»(•< ill aiiiiiire.K.th>ii iivioss iirain (n) and shearing u-ith grain. 
[PouBds per square inch.] 



Species. 



Iteduced to 15 per cent moiittire. 



Loiigleaf pine, 
f'libanpine .-. 
Shortleal" ]»iue. 
Loblolly pine. - 



Reduced to IL' per cent moisture. 



White pine 

Red pine 

Spruce i>ine 

Bald cypreea 

While'cedar 

Doiiiilas 8pruc©6. 

AVhiteoak 

Overeup oak 

Po.st oak 

Cow oak 

Red oak 



Num- 
ber of 
t«sts. 



Compres- 

Bion 

across 

grain. 



1,210 
400 
330 
690 



130 
100 
175 
650 

87 

41 
218 
216 

49 
256 

57 



Shearing ! 
with 1 1 
grain not 'jj 
reduced 

for 
moisture. 



1,000 

1,000 

900 

1,000 



700 

1,000 

1.200 
8110 
700 
800 

2, 200 
1.900 

3, out) 
1,900 
2,300 



700 
700 
700 
700 



400 

500 

800 

.WO 

400 

500 

1,000 

1,000 

1,100 

900 

1,100 



If. 
17 
1 18 
19 
20 
21 
1 22 
1 23 
24 
25 
26 
27 
28 
29 
30 
31 
32 



Species. 



Redxiced to 12 per cent moisture — 
Continued. 



Southern red oak . . . 

Black oak 

"Water oak 

"Willow oak 

Spanish oak 

Sliagback hickory. 
"White liiflvory — 

"Water hickory 

Bitternut hickory. 
Nutmeg hickory -. 

Pecan hickory 

Pignut hickory 

White ehu 

Cedar elra 

"White ash 

Green ash 

Sweet gum 



Num- 
jer of 
tests. 



Compres- 
sion 
across 
grain. 



117 

40 

30 

153 

255 

135 

75 

14 

23 

72 

37 

30 

18 

44 

87 

10 

118 



2,000 
1,800 
2.000 
1,600 
1,800 
2,700 
3,100 
2,400 

2. 200 
2.700 
2,800 

3. 200 
1,200 
2,100 
1,900 
1,700 
1,400 



Shearing 

with 
grain not 
reduced 

for 
moisture. 



900 
1,100 
1,100 

900 

900 
1,100 
1,100 
1,000 
1,000 
1,100 
1,200 
1,200 

800 
1,300 
1, lOO 
1,000 

800 






oTo an indentation of 3 per cent of the height of the specimen. 



b Actual tests on "dry " material not reduced for moisture. 



Having fully established tlie great influence of moisture on the strength of wood, the practi- 
tioner still needed information as to the rate and manner of drying and as to the way in which 
moisture is distributed during seasoning. Several thousand moisture determinations were made 
and it was established beyond doubt that moisture is generally least abundant at the ends, is 
quite evenly distributed throughout the length, but i.s not always uniform in different parts of the 
.«ame cross section, often varying in this respect within astonishing ranges, so that the use of 
timber in a half-seasoned condition, and where uniform seasoning can not be obtained by the 
material, requires that these facts be duly considered in designing. 

Tests of Maximum Uniformity. 

Both in this country and abroad small differences in strength values were often interpreted 
as deciding for or against any given material. This same problem arose also in every case where 
many results were to be compiled, and it seemed especially desirable once for all to find just how 
much uniformity could be expected of wood materials. From a large series of well-selected 
quarter-sawed pieces repre.senting several kinds of pine, cypress, and hardwoods it was found 
that even contiguous blocks, 2.J inches long, may differ by as much as 2 to 4 per cent in conifers 
and as much as 13 per cent in oak, and that in a scantling only (i feet long the butt might differ from 
tbe top by 10 to 20 per cent in conifers and over 35 per cent in oak. This extremely valuable set 
of results throws much light upon discussions of the past, and is well suited to show that many 
boastful claims rested on very flimsy and entirely unreliable differences, such as might well be 
accounted for by a little more extended examination of materials. It will also assist in judging 
test results in the future and help to avoid useless controversy and prejudice. The following 
more lully illustrates the results of this series: 

Scantlings of air-dry material, 6 to 10 feet long, of white pine, longleaf pine, tuliptree (poplar), and white oak, 
and of perfecUy green material of loliloUy pine and cypress, fresh from the saw, were cut partly into blocks 2 by 2 
by 2i inches, bur mostly into cubes of 2| inches. All material was quarter sawed, carefully prepared, and in all 
cases treated alike, either perfectly green or dried together at the same temperalnre. Altogether 529 tests in 
endwise compression were made, namely, 100 ou white pine, 72 on longleaf pine, 99 on loblolly pine, 10 on white 
oak, 115 on tuliptree (poplar), 103 ou cypress. 

H. ])oc. 181 24 



370 



FORESTRY INVESTIGATIONS TT. S. DEPARTMENT OF AGRICtJLTURE. 



From these tests the following table of averages is ilcrivnd, together with tig. !I7: 

Average of testa for maximum uniformity. 



Namir. 



"White pine (Finns strohna) 

Longleaf pine (Finns palnslris) 

Tuliptree (poplar) (Liriodendron tnlipifera) 

White oak (t^nerene allia) 

Lohlolly ]iiue (Finns t.;eda) 

Cypress (Taxodinm distiehnm) 



Moisture, 



Per cnlt. 
8 

7.8 

8 

Yard dry. 

125 + (green). 

125 + (green). 



Average 
strength of 
all pieces. 



(Ireatest difference in 
strength hetween a<l.)oin- 
ing pieces. 



Urn. per sq. in. 
4,900 
10, 800 
(i, 010 
8,300 
2,670 
4,090 



J^bs. per sq.in. 
190 
;i80 
480 
1,110 
130 
70 



Per ceiit. 
3.8 
3.5 
8.3 
13.4 
4.8 
1.8 



Greatest dif- 
ference in en- 
tire scantling. 
i. e., 6-10 foot 
piece. 



/Vr cent. 



18 
10 
20 
37 
20 
IS 



It will he observed that green cypress excelled in its uniformity; that green lolilolly jiroves not more uniform 
than dry white and longleaf pine; that wood of the conifers far excel even the tuliptree (poplar) with its uniform 
grain and texture; and that oak, as might be expeitod, is the least uniform. It will also lie noticed that even iu 
one and the same short scantling (6 to 10 feet) of select quarter-sawed longleaf pine dili'erences of 10 per cent may 
occur, and that iu all others the.se dift'erences were even greater. 

Incidentally in this and the following experiment a small number of the blocks were thoroughly oven-dried 
(to about 2 per cent moisture), and it was found that the strength of both cypress and loblolly was increased by 
about 150 per cent during drying, so that wood at 2 per cent is about two and one-half times as strong as perfectly 
green or soaked material; and also that drying from 8 to 10 per cent to the lowest attainable moisture condition 
(\ to 2 per cent) still adds about 25 per cent to the strength of the wood. 

In the following diagram and table a part of the results are presented in detail : 



//ooo. 




2.000 
fflOC/fJVl/Mfffff:/ 3 5 7 9 // /3 /S /7 /9 2/ 23 25 

FiQ. 97.— strength of contiguous blocks, showing; masiuium uniformity of select (quarter-sawed material in compresaion endwise. 



TIMBER PHYSICS VARIATION IN STRENGTH. 

Strenylh of contiguous blocks of the same scantlinij, select material, in compression endwise. 
[Dimensions generally, 2.76 by 2.7C by 2.76 inches.] 



371 



Xllinl»'r of blocks. 



8- 
9. 

10. 

11 . 

12. 

13. 

14- 

l.'i. 

16. 

17- 

18- 

19. 

20 . 

21- 

22. 

23. 

24. 

25. 

26. 

27. 

28. 

29. 

30. 

31. 

32. 

33. 

34. 

35 . 

36 . 
37. 
38- 
39. 

40 -, 

41 -, 

42 -. 
43.. 
44 .. 
4.'; . . 
46 . 
47.. 
48 -. 
49.- 
50.. 
51 -. 
52.. 
53.. 
54-. 
55.. 
56-- 
57.. 
58-. 
59.. 
60.. 



Kind of wood. 



White 
vine (8 
jier cent 
mois- 
ture). 



Longleaf 

pine (8 
per cent 
mois- 
ture). 



Loblolly 
pine 

( 125 -f per 
cent 
mois- 
ture). 



Cypress (125-f-per 
cent moisture). 



Tulip- 
tree (8 
per cent 
mois- 
ture). 



Pounds per square inch. 



5,070 

4, 940 

5, 020 
.'■., 110 
5, 020 
4,950 
4,820 
4,950 

4, !I0U 

5, 040 
5, 160 
5,120 
5, 100 
5, 230 
5,280 
5,260 
5, 2S0 
5,300 
5,310 
5. 30U 
6,350 
5. 400 
5.360 
5,360 
5,510 
5,070 
5,150 
5,020 
4,770 
4,770 
4,920 
4, 950 
4,840 
4,860 

£(6,460 



11,580 
11, 530 
11,310 
11,060 
8,250 
10,740 
11,180 
11,220 

10, 980 
11,130 
11.510 
11,490 
11,320 

11, 220 
11,320 
11,340 
11,470 
10, 790 
10, 740 
11,030 
11,110 
11,450 

12, 250 
12,760 
10. 740 
10, 360 
10, 280 
10, 150 

9,860 
10, 000 
10, 120 
10, 370 
10. 320 
10, 250 
10.400 
10, 050 
10, 060 
10, 350 
10, 100 
10, 030 
9,970 
9,880 
10, 050 
10, 220 
10, 470 
10, 860 
10, 590 
10, 350 
11,150 
10, 970 
10, 890 
10, 790 
10,970 
11,040 
10. 940 
10, 970 
10, 840 
10,710 
10, 890 
10, 710 



2, 330 

2,380 

2, 380 

2. 4,50 

o 5, 700 

2, COO 

2. 080 

2. 640 

2, 720 

a 6, 970 

2, 770 

2, 7:ill 

2,780 

2,800 

a 5. 840 

2,880 

2,870 

2,870 

2,860 

a. 6, 480 

2.760 

2, 760 

2,720 

2. 640 

a 7, 050 

2,680 

2,660 

2, 650 

2,780 

a 7, 320 

2, 730 

2, 780 

2,720 

2,660 

a 6. 360 

2,010 

2,560 

2,680 

2, .580 

a 6, 220 

2,020 

2, 601) 

2, 640 

2,610 

a 6, 440 

2, 620 

2, 621) 

2. 600 

2,080 

a 6.440 

2, 710 I 

2,7.50 

2, 700 

2, 720 

a 6, 850 

2.710 

2,660 

2. 800 

2,660 

a. 7, 030 



2,720 
2,700 
2.720 
2,680 
2,680 
2. 720 
2,770 
2, 820 
2, 870 



3,020 
3, 070 
3, 099 
3, 120 
3. 171) 
3, 140 
3,090 



3,120 



3.170 
3, 220 
3, 270 
3, 320 
3,270 



3,320 
3,370 
3,420 



4,170 
4,190 
4,170 
4,180 
4, 200 
4, 18U 
4, 230 



i 



4,230 
4,180 
4,130 
4,160 
4,160 
4, 100 
4,110 
4,090 
4,070 



5.740 
5,700 
5,770 
5,700 
5,430 
5,430 
5, 420 
5, 500 
5. 440 
a 7, 070 

5, 770 

6, 030 
6,170 
5,840 
5,440 
5,360 



3, 490 
3, 520 
3,570 
3,620 
3,640 



5,530 

6, 530 

a 6, 880 

5. 920 
5,930 
5,770 
5,780 
6, 120 
6,480 
6,310 

6, 221) 
6,310 

n7,420 
6,340 
6,360 
6,040 



6,280 
6,490 
6,610 
6.220 
6.190 
a 7, 300 
6,010 
6,140 
«, 170 
6,010 
0,490 



6,080 
5,860 
6,110 

a 7, 920 
6,210 
6,270 
6,300 
6,420 
6,460 
6, 170 
6,440 
6, 340 
6,310 

O7,540 



Oak 
(yard 
dry). 



9,970 
9,370 
8,260 
8,120 
8,120 
8, 480 
9,160 
8, 500 
7, 58U 



6, 910 

7, 340 

7, 870 
8, 900 
9,130 

8, 380 
7.890 
7,840 
8,480 



9,030 
8, 660 
8,060 
7, 740 
7, 680 
8,400 
8.710 
8,060 



7, 280 
7,510 
7,510 

8, 080 

9, 030 
8,790 
8,640 
8, 560 
8,780 



II Dried to about 2 per cent moisture before testing. 

As was indicated at the outset and is fully explained in Bulletin.s f". and S, the plan of this 
investigation also included among the objects to be sought the establislimeiit of the following: 

(1) The relative value of each species. 

(2) The outward .signs or physical and structural properties, easily used in inspection. 

(3) The relation of the properties among themselves; and 

(4) Their relation to the conditions under which the wood is formed, such, for instance, as the 
age of the tree when wood is laid on, iutluences of soil, climate, etc. 

As has been explained, some of these relations were more or less fully determined, at least, 
qualitatively; nevertheless, the relation of the several forms of resistance, as well as the mutual 
relations of the properties iu general, seemed to escape observation in the manner of inquiry 
generally pursued. It became clear befo-e long that these laws must be established by special 
series, planned each to seek answer to some .specific question. Several of these were carried out, 



372 POKESTEY INVESTIGATIONS V. S. DEPARTMENT OP A(;UU'Ul/rURE. 

and, thouga little more was accomplished than to find proper ways, the study oC these results, 
amplified by the large ordinary serieg, led to several iuterestins' discoveries, the most important 
of which is the discovery of the relation between the strength in cross bending at elastic limit 
and the compression endwise, this latter being equal to the fiber stress of the former. Though 
still requiring special experiments to become convincing, it is fair to state at this i)oirit that a 
great deal of useless testing will be saved in the future, since the test in compression is by all 
means the simplest, the selection and treatment of the material for it the easiest, and the result 
the most satisfactory. The importance of this discovery by Mr. R. T. Neely is such that a reprint 
of Mr. Neely's discussion here will be found. justified. 

Kei.atiox ok CoMrRES.siON-ENDWisE Stuenoth TO Hrkakinc LoAi) oi- Beam. 

In testing timber to olitain its various coefficients of strength, the test ■which is at once the simplest, most 
cx]ieilieut, satisfactory, au<l re,lial)le is the "comjiression-endwise test," whicli is made by crushing a specimen 
|iarallcl to the fibers. All other tests are either mechanically less easily performed, or else, as in the case of cross- 
bending, the stresses are complex, and the unit coefficient can be expressed only by reliance upon a theoretical 
formula, the correctness of which is iu doubt. It would, therefori', be of great practical value to tind a relation 
between the cross-bending strength, the most important coefficient for the jiractitioner, and the compression strength, 
when the study of wood would not only be greatly simplified and cheapened, but the data could be applied with 
much greater satisfaction and safety. 

The consideration of su<h a relation resolves itself naturally into two parts, namely, a stndy of the relation ot 
the internal stresses in a beam to the external load which produces them, and a study of the relation of the internal 
stresses in a beam to the compression-end wise strength of the material of which the beam is made. 

The first relation has been a subject of study for more than two centuries, and from the time of Galileo down to 
the present day the theory of beams has been gradually evolved. Within recent years several eminent physicists 
and engineers have given a true analysis of both tlie elastic and ultimate strength of a beam, a clear exposition of 
which is made by Prof. J. B. .Johnson in his work on Modern Framed Structures. He points out that the "ordinary 
I ([nation " for obtaining the extreme liber stresses, when the external load and dimensions of the beam are given, is 
not applicable to a beam strained beyond its elastic limit; and he follows this statement with a discussion of the true, 
distribution of internal stresses in a beam at time of rupture, and with a " Rational eciuatiou for the moment of 
resistance at ru))ture," devised by M. .Saint- Venant, which re,ally does connect the extreme liber stress in abent beam 
with the compression-endwise strength and also with the tension strength. Professor Johnson's final conclusion, 
however, is that for practical use the " ordinary formula" maj^ be applied to ,a be.am at rupture, providing the fiber 
stress involved is obtained from cross-bending tests; and this is the present practice among engineers. 

RELATION OV INTERNAL STRESSES. 

Assume for the discussion of the relation of internal stresses to external lo.-id the sini]>le conditions of a lieam 
of rectangular cross section loaded at the middle. 

Regarding the distribution of internal stresses, it must be agreed that the neutral plane lies in the center of the 
beam so long as the beam is loaded within the elastic limit ; this follows from the fact that the modulus of elasticity 
is the same whether derived from com.preBsion tests or from tension tests (i. e., Ec = Et), as proved by experiments 
of Niirdlinger, Bauschiuger, Tetmayer, and others. 

Since the distortion of any given tiber in the beam is proportional to its distance from the neutral plane, the 
distriluition of stresses in a longitudinal section of .a beam loaded up to its elastic limit may be represented by the 
followiug diagram, iu which the vertical scale represents increments of distortion and the horizontal scale the liber 
stresses. 

In this diagram the angle a = angle h, since E<. = Et ; ami furthermore, since these latter quantities are each 
equal to the modulus of elasticity obtained from cross-bending tests (.according to the same authorities), this angle 
a (or h) van be obtained by platting the results of the cross-bendiiig test itself. 

It is a wellestablished fact that the tension strength of wood is much greater than the compression strength, 
,an<l also, as shown by the German experimenters quoted, that the elastics limit in either case is not reached until 
shortly before the ultimate strength. Purthermore, it seems reasonable to suppose, and is essential to the construc- 
tion of the above diagram, that the true elastic limit of the beam (shown on the strain diagram of a beam at the 
])oint where it ceases to be a straight line) is reached at the same instant that the elastic limit of the extreme com- 
pression tiber is reached ; for when the loading is continued beyond this latter conditi(m the line OC must begin to 
curve upward (since the proportion of load to distortion on that side begins to increase more rapidly), while the line 
OT continues in its original direction. Therefore, in order to maintain the equilibrium, the whole distribution of 
stresses will necessarily be changed, the position of the neutral axis will be lowered, and these changes will, of 
course, show an eS'ect on the defiection of the beam. 

Now, eveu .at rupture the proportionality of fiber distortion to distance from neutral axis is maintained (because 
a plane cross section will always remain a plane), and therefore the distribution of interual stresses just at the point 
of rupture can be represented by a diagram similar to tig 99, in which, as before, the vertical scale represents incre. 
ments of distortion and the horizontal scale fiber stresses. The fibers on either side of the nentr.al plane are under 
stresses which vary from zero at the neutral plan<' to the maximum stn-ss iu the extreme liber, changing in proportion 



TIMBER PHYSICS RELATION OF CRUSHING TO BENDING. 



373 



as the increments of load iu the test machine vary. Therefore, the distributiou of stresses on the compression side 
of the neutral plane will be shown by an ordinary strain diagram for compression, and on the tension side by a 
similar tensiou-straiu diagram. Unfortunately there are no reliable diagrams of these kinds now on record. The 
compression pieces tested have usually been too short to afi'ord reliable measurements of distortion, and, owing to 
structural and mechanical difficulties, satisfactory tension tests seem to be impossible. 

.Sr/?£SS£S /A/ /,000 LBS. 
U. / 2 3 4 S 6 



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Fiti. 98.— Relation or fiber stresses and diatortion:*. 





\/y. 


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, , ^ 


1 1 1 1 1 1 1 1 
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^ S 6 7 3 ^ /Oy/ 



Flo. 99.— Distribution of internal stresses iu a beam at rupture. 



Experience iu testing, however, has taught that when a piece of green wood is tested in ^ompre88ion it will 
undergo a great distortion after the maximum load has been applied without actually biealcing down — in fact, while 
sustaining the same load. A piece tested in tension, on the other hand, breaks suddenly as -ioon is the maximum 
load is applied. A beam iu failing may, therefore, sustain an increasing load long after the extreme compression 
fiber has been loaded to its ultimate strength; the fibers on the compression side continue to be mashed down, 
while the ueutral plane is lowered and the stress in the tension filter increases until, very often in practice, the beam 
"fails iu tension." With these facts and 



^ 



rO/RC£S 
L 2 3 4 S 



//V 
S 7 



WOO 
8 9/0 



LBS. 

// /a 



observations before us it is possible to con- 
struct a diagram so that it will represent, 
approximately, at least, the distribution of 
internal stresses iu a beam at rupture. (See 
fig. 100.) 

In this figure OA represents the position 
of ueutral plane at time of rupture, OU the 
distortion in the extreme compression fiber, 
UC the stress on same fiber, OL the distor- 
tion in extreme tension fiber, and LT the 
stress on that fiber. 

It can readily bo seen that the manner 
of breaking will influence slightly the form 
of this diagram. If the beam falls in com- 
pression before the tension fiber reaches its 
elastic limit the line OT will be straight as 
shown, otherwise the line will assume some 
such positiou as Oi,T, (diagram 99), iu which 
/, is the elastic limit iu tension. 

From the approximate distribution of 
internal stresses their relation to the external 
load may be determined. The two funda- 
mental equations — (1) that the sum of inter- 
nal stresses on the tension side equals the sum 

of internal stresses on the compression side, and (2) that the sum of the external moments equals the sum of the inter- 
nal moments — apply at the time of rupture as well as at the elastic limit. From (1) it follows that area OUC?=^area 
OLT, and the jtosition of the neutral plane at rupture is thereby fixed. If now the line LU be assumed to represent 
the depth of the beam iu inches instead of indicating the distortion of the fibers, the sum of the internal moments 
about the point O is found by multiplying the area of either the compression or tension diagram by the sum of the 
distances of their respective centers of gravity from the neutral plane. By putting this sum equal to the motiient 
of the external load about the same point O the first relation is established. 




Fig. 100. — Position of neutral axis and internal stresses at rupture of beaui. 



374 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 

RELATION or CRUSHINU-KNDWISE STRKNOTU. 

The secoud relation (that of crushiiiK-endwise strenstli to iutonial stressos) was touched upon iu discuasinj; the 
first, whiu it was stated: (1) That the true elastic limit of the beam is j)i()lial)ly rcachud at the same instant that 
the extreme libers on the compression side reach their elastic limit in cDmprcssiou. (2) That this latter limit lies 
close to the ultimate compression-eud wise streu^tli (so close that former experimenters have been unable satisfactorily 
to separate them). (:i) That a piece of gieen wooil will stand a ^rcat deal of distortion after the ultimate load is 
applied before actually failing. And to these statements may be added the evident fact (4) that the stress on any 
fiber on the (•onipressiou side can not exceed the compression-endwise strength of the material. (5) Finally and 
most im])ortant it appears from (1) and (2), but especially from an examination of the several thousand test results 
on tlie several species of conil'crs made by the Division of Forestry, that the extreme fiber stress at the true elastic 
limit of a beam is practically identical with the compression-endwise strengtii of the uuiterial. (This last observa- 
tion, which was forced upon the writer by its continual repetition in the largo series of tests under review, lies at 
the basis of this discnssion.) The observation of this identity makes the distribution of internal stresses appear 
more simple than was hitherto assumed, and the desired relation between compression and cross-bending strength 
capal)le of matlu'matieal expression. 

DEVELOPMENT Of FORIIUL.E. 

From these considerations the distance UC in fig. 100. which represents the ultimate compression-endwise 
strength of the material, becomes practically equal to the distance el, which represents the compression strength at 
the true elastic limit, and hence the line IC straight and vertical; and if OT is taken as straight, the diagram will 
be made up of simple geometric figures, as in iig. 100. 

The line LU will represent the total fiber distortion at time of rupture, and is equal to the sum of the amounts 
by which the extreme compression fibers shorten and the extreme tension fillers elongate. 

Let a test in which the following (luantities have been observed and recorded be considered : 

Let Pr= the external load at rupture (pounds). ^ 

^r^the corresponding defiection of the beam (inches). 
C = compression-endwise strength of the material (jiounds). 
E^ modulus of elasticity (pounds). 
rf=:de])th of beam (inches). 
6 = brcadth of beam (inches), 
i^ length of beam (inches). 
zJe^detlection at true elastic limit. 

Then, based upon the above statements, by means of formulas derived from the geometric relations of the diagram 
and the fundamental eijuations of equilibrium, the following ([uantities can be eaUiilated: 

Let t',,=; total liber distortion due to bending at true elastic limit (inches). 
Er-i= total fiber distortion due to bending at rupture ^:Llj (inches). 

(Jp^ distortion in extreme tension fiber at rupture = LO (inches); also the proportional dis- 
tance of neutral plane from tension side of beam. 
(Jr^real <listance of neutral j)lane at rupture from tension side of be;im (inche.s). 
rf,. = real distance of neutral plane at ruptuie from that fiber on compression side which has 

just reached the elastic limit, in inches = 0e. 
T^ stress in extreme tension liber (pounds). 
T„ = 8um of forces on tension side^area OLT (pounds). 
Ca=sum of forces on compression side = area 011(1/ (pounds). 
fZt = distance of center of gravity of tension area from neutral plane (inches). 
(J;. ^distance of center of gravity of compression area from neutral plane (inches). 
Mr^sum of the internal moments about the point O (inch-pounds). 

The formulas connecting these quantities are derived as follows: 

To find Eo let tig. 101 represent a portion of the beam one unit in length bent to its elastic 
limit; then, 

Fia. lOL— riljor dis- 1 •■ ' 

tortioii in unit 

length of beam, at where r is the radius of curv.-iture, but from. fundamental formulas true at elastic limit 
elastic limit. 

_ 1 _ m _ VI __12.^6 „ __ 12zl,d 

(•~Er~4ET~ P .-.{1)^,— p . 

Since this involves only geometric relation.s, it is true also at rupture (since the beam preserves its original form). 

(2) K. = -^^. ■ 

To find (/j, and T : 

Since the sum of stresses on the tension side i=sum of stressc^s on compression side, 

rf„ EeC rf„C 

the area OLT = area OUC ? . ■. J T = ( LV — dp) C ^ and T = , g-^ 




TIMBER PHYSICS — RELATION OP CKUSHING TO BENDING. 



375 



from the similar triangle OLT aud Oel (tig. 100), 



^^ _(£r-<ip)C-^«C, 



Ee 



whence, 

(3) d^=VErXEe — ^' 
aud after d„ is found, T can be obtained : 



(4) T = 



rfpC 



Now, when the vertical Hue LU is assumed to represent the real depth of the beam in inches = <f, every verti- 
cal nieasiiro will be cliauged in the ratio y (see tig. lOL') ; whence, 



(5) dr = j^df, 
(real distance of neutral plaim from tension side). 

(b) d„ = + ^Eo 

(jj because t'c total distortion, while d,. is the distance 
on one side of the neutral plane). 

The area OLT would then become : 



z/ 



c 



(7) T. 



d/r 



aud the area OUCi = 



(Jo 



(8) Ca=((? — rfr)C — (g XC) 

(C» must equal T,). 

The distance of centers of gravity would be 

(9) <i, = jdr, 

d — dr, d„ 







(10) (l,- 



2 



'+':• 





A 

\ 
t 
I 

\ 

■ 


I 


[ d 


.^-^"^"^^ /V£UT/?AL PIANE 


^^^^^^^ 4 


\^-~^ V 



and thfe sum of internal moments. 



Fio. 102.— I'ositiou of neutral piano at rupture. 



T 



= ilfr = C.((Jc+<it)*. 



(11) Jlf,= (C«dc + Ta(«t)'', and Kiuec C» = T„ hence J/,= C.(dc-f <it)6. 

But since the .sum of iuternal moments equals the sum of external moments: 

4 ' 

And since Pr is the brenkiuu; load of the beiim, and Ca involves only the compression endwise strength and lineal 
dimensions, we have a formula directly connecting the breaking load of a beam with the compression strength.' 

Application of these formula'. — Unfortunately no tests have been made to study the application of these formnlai 

directly and in particular. The tests on beams published in this cirCTilar were made lor a different purpose. For 

the purpose of ascertaining the correctness of the formuUe only the tests made on large beams have been utilized, 

since in these the deflections were specially accurately measured. In addition to the quantities to be calculated 

already given in this discussion, the liber stress at the true elastic limit is also calculated, aud called Se, to be 

compared with C, and the load producing it, Pc, is also set down as an observed <[uantity. If the modulus of 

S P 
rupture, R, has already been calculated by the "ordinary formula," Se can be obtained from the relation-^ ^^^p" "'"^ 

(12) S„=p^E. 

The modulus of elasticity at true elastic limit E,. is recomputed as a check, aud of course is: 

(13) E.=,^^. 

Since Pi is an arbitrary (juautity within certain limits, and can not be determined with any degree of accuracy, 
Sii will be found to dilfer more or less from C. For these reasons, however, C is a more reliable value for the true 
elastic limit than S^ itself, and in the formulie is used as such ; for instance, K,. is the fiber distortion produced by the 
same load which produces a fiber stress = C, not by the load which produces St.. 

The following table exhibits the results of applying the formulEe to the data from these tests: 

['The factors d,-+dt, within such limits as the cross-bending strength is constant, are constants; they will have 
to be ascertained by actual experiment for each species .and quality, and might then be expressed as a proportion of 
the depth. In the material used, pine as well .as o.ak, it appears to be about 3/5. The material on which this rela- 
tionship has been mainly studied was green wood, and it may be questioned whether the factors rf,. and dt would 
rouuiin the same iu material of all moisture conditions. There is uo logic which would lo.ad us to expect a dift'erence 
greater than the limits of "maximum uniformity," i. e., 10 per cent. A few comparisons of data obtained from 
material of other species with varying moisture percentage indjcatie that a, differeftce ^oes not existi — B, E, y.] 



576 



FOKESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGKIGULTURE. 



-;; a 



s 

a 

« 
.0 

V 


-..is-S . 1 . . 1 


■3 
13 


1 - 


SSr-Jooaic>=;^OC4'-'ca 


Distancf 
from net 
tral plan 

of center 
gravity 




CQ'«*-*'i'-»??"*'^-1'-i"-*"*'^ 


•■B^xe aoib-no^ jo 


S3S£SS;SSSS2?2S5B 


eo«Nco'c^corteoMcoC'ieiim 


ili 


'dptS lI0I6fJ9Jdui09 UQ 


d 


i 


23, 300 
22, 760 
27, 400 

24, 000 
25,010 
24,900 
22, 600 

27, 600 
30, 500 
18, 000 

22, 200 

28, 100 

23, 600 


•gpiB iinit^uo) U() 


H 


23, 400 

23, 053 
27, 100 

24, 000 
24, 800 
24. 600 
22, "00 

27, 600 
30, 500 
18, 000 
22, 500 

28, 100 
23, 900 


■jaqg 
aoieua^ (»ui9JiX9 jo dJiudnj jb bbsjis 


T 

Lbs. per 
sq.io. 

9,700 
9,810 
12, 200 
9, 800 
9. 920 
9,820 
8,350 
11, 300 
11,500 
6,780 
11,000 
11,330 
10,400 


Real dis- 
tance of 
neutral 
plane at 
rupture. 


isnl' yirq 1[0!11a\. op!s uoi9 
-s^jdoio.) «o J9qi| ^tiq^ oioj^j 


-c 


[ 






P3 M fh ,-. cj f i c^i — c-i ci ^ f rH 


nreaq jo 9pi« aojsttgi uioj^ 


■« 




.^.^^^iftuiin^'uSif. rfT^^ 


•.».innliu 
jB .umy uoiKU^i kiiiinj)X9 ui uin)JO(«!(i 


■0' 


-,■ t~ oo -.D ,0 cc .r eo in =: r- t^ 

o=>oo-,c 000=0^ = 
0000000000000 


oooo'oo'ooodo"dd 


VJUUJI 


«• %J 




Total fiber dis- 
tortion due to 
bending. 


•gju^dnj %Y 


0. 




O^QOO-t?liftCDOr^O 
Mffl.*tOU5lOOt~iO.-i-^QOO 

0000000000000 


"\\m\\ o\%9V\9 lY 


H 


0039 

0055 

0059 

0054 

0053 

0058 

0046 

0055 

0062 

050 

0059 

0060 

0050 


1 


0000000000000 


'inmioi'iv 


'«[9 enj) IB qiSa9J'}e Satpaag^ 


'^ »3 e^'v-ii''^'-*'^'"'^ ..-r&i©rwi05 


•a.nil(luj iv, 
(J (iiind jnoqu 8|U3mom iBu-iajai jo rang 


a ! ="50 •!»«o*r.f •T*;ii«*»»»'f 


1 
a 

--> 

a 

1 


'Ojn^duj IB itaiod 
)uoqii s!)a9uioui [Biud^xd j6 nine xitn^ay 


51" 




''\\01l\ Ot^SBp eUJ') fB aOI)3909(£ 


<j 


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o.-c 0000 O' 000000 


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OOMOO.HCSOO.-.OJOOP3 


t-0000CO00t~00t-a)t-000000 


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M M ^J CI «C CI 
t-l CI ^ r., ^ M M W CI ,-1 CI 01 


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1 


« to <i-^ ■*">*■» in ".jfrot~io« 


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•iunidnj ^u pBOT 


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1 88ggs§S3SSggg 

1 oinco^ooift ■^■Mtct-ooifto 


1 N (M rt (M M C) M 5-1 .X r- .-^ CI 


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tot~o-*w — m^Hloo^~■T»■^-. 
rttoco■^fl«p■v-ft~x^clrt(Dco 


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1.3 




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ii D S C G 5; ::; rt c D 

tQPaPPQOTf.- -pp 

S i3^5 



TIMBER PHYSICS METHODS. 



^77 



In Older to see how far the lormule may he appliciihle to beams of the same material the data obtained on the 
small beams cnt from one of the largo beams were subjected to scrutiny, basing the caleulntions on the data from 
the ad.ioiniug comiiression block. The calcnlated result compareil with the actual breakiiiu,- load showed a most 
convincing similarity, as will he apparent from the table herewith presenled: 

Sdrmith of small he.aws, calcnlated b,j Keeh/s formiilw from comprts.vicH s/rcnoth, on. Ihc <,s«nnq,tion that the rdatin: 
position of the nentral itlaiie ni rnpturi; is the same as fonnd in large beams. 

[Shortleaf pine, large beam No. 13, special series. 1 





Data observed in testing. | 


Results calculated by Neely's formulje. 


s 

Si 

O 
u 

3 
a 


t 

Dimensions of 
beams. 


Bending strength as calculated by ordi- 
nary formula. 


© 
a 

1 
p. 

a 

o 
O 


P. 

© 
en 

O 


Load at rupture, as calculated by Neely's 
formula, from conii)resBiou strengtb. 


a 

1 

(S 

a 
£ 

M 

a 


Eeal dis- 
tance of 
neutral 
plane at 
rupture. 


a 

o ® 

i 

U3 


Sums of forces 

for unit width 

of beam. 


Distance 
from neu- 
tral plane 
of ceutcj- of 
gravity. 


O 
P 

I 
g 

p£ 

if 

g 

3 

£ 


a 

a 

© 
u 

Ed 
a 
& 


a 
•| 

a 

3 

i 

a 
_o 

o 
© 

P 


bo 
© 

I 






o 

© 

n 
o 

1 

i 


p- ■ 

« 2 
o o o 

111 

«^© 

1i1 

£ « t. 


© 

C3 
© 

a 
O 


© 

=3 
_o 

1 

P. 

a 

o 
o 

3 


a 
1 

o 


C3 

£ 
§ 

'i 

g 
p, 

a 

O 

S 


d 


b 


K 


c 


P 


Pr 


S. 


d. 


& 


T 


T. 


c. 


A 


M. 


P. 


A, 
Inch. 


Incbes. 


Lbs. per sq. in. 


Lbs. 


Lbs.per 
sq. in. 


Incbes. 


Lbs.per 
sq.ln. 


Lbs. 


Lbs. 


Inches. 


Inch 
pounds. 


Lbs. 


2 
3 
4 
5 
6 
7 
8 
a9 
10 
11 
12 


50 
50 
50 
50 
50 
50 
50 
50 
50 
50 
50 


3.51 
3.75 
3.55 
3.49 
3. .58 
3.53 
3.56 
3.52 
3.52 
3.47 
3.48 


3.56 
3.37 
3.6U 
3.50 
3.54 
3.50 
3.54 
3.54 
3.45 
3.52 
3.54 


7, 3.50 

7. ■.no 

7,790 

8, '-'SO 
7, 750 
7.810 
7,470 
5, 13U 
7,510 
6,370 
6,580 


4.430 
4.61(1 
4,.'i60 
4,070 
4.1.50 
4,160 

s,s;o 

3,SS0 
3,680 
3.7.iO 
3.540 


4,300 
.1,000 
4.710 
4,680 
4.6!>0 
4,. 540 
4,470 
3,000 
4,'JSO 
3,600 
3,760 


! 4,708 
5.3 lO 
5,057 
4,-J03 
4,571 
4.4-JO 
4,578 
4,169 
3.854 
3,3 1-i 
3.«1»7 


3,760 
4,430 
3,969 
4,-2-20 
4,296 
4,129 
4,178 
3,078 
3.860 
3,8»S 
3,395 


1.46 
1.56 
1.48 
1.45 
1.49 
1.47 
1.4S 
1.47 
1.47 
1.44 
1.45 


1.23 
1.31 
1.24 
1.-22 
1.25 
1.23 
1. 25 
1.23 
1.23 
1.21 
1.22 


10.517 
10. 979 
10.885 
9, 675 
9,894 
9,943 
9,104 
9,274 
8,796 
8,926 
8,415 


7,677 
8,564 
8, 1155 
7,014 
7,371 
7, 30« 
7,381 
6, 810 
6,465 
6,427 
0,101 


7,719 
8,552 
8,026 
7,061 
7,376 
7,290 
6, 840 
6.751 
6, 403 
6,485 
6,124 


0.97 

1.04 
99 
0.97 
0.99 
0.98 
0.99 
0.98 
0.98 
0.96 
0.97 


1.18 
1.26 
1.19 
1. 17 
1.20 
1. 18 
1.20 
1.18 
1.18 
0.87 
1.17 


58,760 
66, 380 
63, 216 
52, 535 
.57, 144 
.55, 248 
57. 222 
52,118 
48, 177 
' 41, 400 
46,219 


2,200 
2,800 
2,400 
2,400 
2, 600 
2, 400 
2, 500 
1,800 
2,200 
2, -200 
1,940 


0.296 
0.391 
0.413 
0.345 

0. 356 
0.431 
0.440 
0. 328 
0.387 
0.372 
0.300 



a Failed, due to knot. 
Note.— Columns of figures in same distinctive type to be compared one with the otlur. 

On the whole, it is in no way boastful to assert tliat tbis work has already fnruisbed prac- 
tical data euough to uiore than pay the expenses incurred ten times over; that its fruits are uot 
half jiatbered, and that Ibr more than a quarter of a century its results will .serve as a basis for 
the user of wood and as the guide to the teacher and e.xperiiueuter. 

Devklopment of the Science oy Timber 1'iiysics and Methods Employed in the 

Investigation. 

Since the elaborate plan and methods of this study of our woods denotes an entirely new 
departure in timber investigations, at least in our (-ountry, it is only fitting to place the credit for 
its conception, for the elaboration of the plan, the organization of the work, and the persistent 
prosecution of the same in spite of many drawbaidvs and lack of support. This credit belongs to 
Dr. B. E. Fernow, chief of the Division of Forestry. The plan was first foreshadowed in his second 
report (1887, p. 37) as cliicf of that division, ami the word "timber physics" was there used for 
the first time, and the essentials of the future plan were there discussed. In a small tentative 
manner the first steps to put it in operation were made in 1888. In the report for 188!) we read : 

The investigations into the technology of our timbers and especially into the conditions ni>on which the .lual- 
ities of our timbers depend-for which Mr. Roth of Ann Arbor has begun preliminary studies— has also made but 
slow progress for lack of means. 

In the report for 1890 we find, besides an account of tlie tests on Northern and Southern oaks 
referred to before, the statement that "by the increase of ai>propiiations the forest technological 
investigations referred to in former reports have become possible on a scale which was hitherto 
unattainable," and a description of the plans is given. But the first fuller statement of the 



378 KOKESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 

(lev'eloi)iuent of the investigation and its methods was not published until 1892, in Bulletin (i, in 
which Mr. Fernow described the aims, objects, and methods at length. 
In the report for ISOO the following language is used: 

TIMBER TESTS. 

AVliild till' 1180 of woiiil i)ulii mill Dtlier substitutes mi;y displ.icd in many w.ays tlie use of wood iu its natural 
state, tliei'o will always be desirable i|uali(ies inlierent iu tbe latter tbat make its use indispensable. Hence the 
desirability of knowing the qualities of our timbers and, if possible, of kuowinj; the conditions under which the 
wood (lop will de%'elop the desirable qualities. 

iMuch work and useful work is done in the world by the rule of thumb. All such work is not reliable and 
certainly not ecouoniical. With the need of f;reater economy in jiroduction, the need of more accurate measuring 
arises, aud with that the need of more specitic knowledge of the itiaterials to be measured. 

Wood is one of the materials which has been measured by the rule of thumb longer than others. Iron aud 
other metals used in the arts have their properties much more accurately determined than wood material. Especially 
in the United States, when we speak of quality of our timbers, it can only be in general terms; we lack definite data. 

One difticulty in determining reliably the ijualities of our timbers lies iu the fact that living things are rarely 
precisely alike. Every tree differs from every other tree, and the material taken from the one has a different value 
from that taken from the other of the same species. Yet every tree has some characteristics in common with all 
those grown under similar conditions. But even these common properties differ iu degree in different individuals. 
Iii(livi<lual variation tends to obscure relationship. 

The fac-lors which determine the iiuality of timbers are found ilircctly in the structure of the wood, and it is 
po.ssible from a mere ocular examination to judge to some extent what ([ualities may be expected from a given piece 
of timber, although even in this direction our knowledge is very incomplete, aud but few definite relations between 
structure and (luality, or between physical aud mechanical prop<Tties, are established. We know that the width of 
the annual rings, their even growth, the closeness of grain, the length, number, thickness, and distribution of the 
various cell elements, the weight, and many other i)hysical appearances and properties of the wood influence its 
quality, yet the i^xact relation of these is but little studied. Conjectures more or less plausible, suppositions, and .a 
few practical experiences preponderate over positive knowledge and results of experiments. Again we know, iu a 
general way, that structure and composition of the wood must depend upon the conditions of soil, climate, and 
surroundings under which the tree is grown, but there are only few definite relations established. We are largely 
ignorant as to the nature of our wood ciop, aud still more so as to the conditions necessary to produce desirable 
qualities, and since forestry is not so much concerned iu producing trei^s .as in i>roducing quality in trees, to acquire 
or at least enlarge this knowledge mu.st be one of the iirst and most desirable undrrtakings iu which this Division 
can engage. 

Accordingly a comprehensive plan has been put Into o|icration to study systematically our more ini|portaut 
timber trees. 

It will at once bi' understood that as loug as the qualities are to be refeired to the conditions under which the 
tree is grown, the collection of the study nuiterial must be made with the greatest care, and the material must be 
accompanied with an exhaustive description of these conditions. Since, further, so much individual variation seems 
to exist in trees grown under seemingly the same conditions, a largi^ number UMist be studied in order to .arrive .it 
reliable averiige values. For the present it has been decided to study tlie pines, especially the white pine and the 
three .Southern lumber pines. 

In selecting localities for collecting specimens, a distinction is made between station and site. 

By station is understood a section of country (or any plaies within that section) which is characterized in a 
general way by sindlar climatic conditions .and* geological forniiition. Station, then, refers mainly to the general 
geographical situation. Site refers to the local conditions and surroundings within the st.atiou, such as difference of 
elevation, of exposure, of physical properties aud depth of the soil, nature of subsoil, and forest conditions, such as 
mix(<l or pure growth, open or close stand, etc. 

The selectiou of ch.aracteristic sites in each station requires considerable judgment. 

On each site live full-grown trees are to be taken, four of which are to be representative average trees; the 
fifth or "check'" tree, however, should be the best developed tree that can be found on the site. .Some additional 
(est trees will be taken from the open and also a few younger trees. The trees are cut into varying lengths, .ind from 
each log a disk of H-inch height is secured, after having marked the north and south sides and noted the position of 
the log in the tree. 

The disks are sent for examination of the physical and jphysiological features to thi' Michigan University, while 
the logs, aud later on special parts of the disks are to be sent to the test lalioratory of the Washington ITniversity 
of St. Louis. Here, for the first time, a systematic series of beam tests will be uuide and compared with the tests on 
the usual small laboratory test pieces. .Such tests with full-length beams in comparison with tests on small speci- 
mens promise important practical nsults, for ii few tests have lately developed that large timbers .seem to have but 
little more than one-half the strength they were credited with by standard authorities, who reliednpon the tests on 
small specimens. 

From the "check " tree mentioned before onl.y clear timber is to be chosen, iu order to ascertain the ]iossibilities 
of the species aud .also to establish, if possible, a iclation between such clear timber and that used iu gener.al 
practice, where elements of weakness are iutroduce4 by knots and other blemishes. 



TIMBER PHYSICS METHODS AND AIMS. 379 

Au authority ou engineering matters writes regarding this work: 

" Inasmuch as what passes current among engineers and architects as information on th<! strength of timber is 
really misinformation, and that no rational designing in timber can be done until something more reliable is furnished 
in this direction, the necessity for making a competent and trustworthy series of such tests is apparent. This is a 
work which the (iovernment should undertake if it is to be impartial and general." 

A careful record of all that pertains to the history and conditions of the growth from which the test pieces 
come, and of their minute physical e.xamination, will distinguish these tests from any hitherto undertaken on 
American timbers. 

The disk iiieies will be studied to ascertain the form and dimensions of the trunk, the rate and mode of its 
growth, the density of the wood, the amount of water in the fresh wood, the shrinkage consequent ui)on drying, the 
structure of the wood in greatest detail, the strength, resistance, and working qualities of th(! wood, and lastly, its 
chemical constituents, fuel value, and composition of the ash. 

In Bulletin we are introduced to the science of "tiuiber physics" in the following language: 

Whenever human knowledge in any particular direction has grown to such an extent and complexity as to make 
it desirable for greater convenience and better comprehension to group it, correlate its parts, and organize it into 
a systematic whole, we may dignify such knowledge by a collective name as a new science or branch of science. 
The need of such organization is especially felt when a more systematic progress in accumulating new knowledge is 
contemplated. In devising, therefore, the plans for a systematic and compreliensi .e examination of our woods it has 
appeared desirable to establish a system under which is to be organized all the knowledge we have or may acquire 
of the nature and behavior of wood. 

To this new branch of natural science I propose to give the name of "timber physics," a term which I have 
used first in my report for 1887, when, in devising a systematic ])lan of forestry science the alisenci^ of a collective 
name for this class of knowledge became apparent. 

While forest biology contemplates the forest and its oompoiieuts in tlicir living condition, we eom|)rise in timber 
physics all phenomena exhibited in the dead material of forest production. 

The practical application of timber or wood for liuman use, its technology, is based upon the knowledge of 
timber physics, and under this term we comprise not only the anatomy, the chemical composition, the physical and 
mechanical properties of wood, but also its diseases and defects, and a knowledge of the iiiUuences and conditions 
which determine structure, physical, chemical, mechanical, or technical properties and defects. This comprehensive 
science, conceived under the name here chosen, although developed more or less in some of its parts, has never yet 
been dignified by a special name, nor has a systematic arrangement of its p.arts been attempted before. It comprises 
various groups of knowledge derived from other sections of science, which are neither in themselves nor in their 
relations to each other fully developed. 

While plant physiology, biology, chemistry, anatomy, and especially xy lotomy, or the science of wood structure, 
are more or less developed and contribute toward building up this new branch of science, but little knowledge exists 
in regard to the interrelation between the properties of wood on one side and the modifications in its composition 
and structure on the other. Even the relation of the properties of various woods, as compared with each other, and 
their distinct specilie peculiarities are Imt little explored and established. Le.SB knowledge still exists as to the 
relation of the conditions which surround the living tree to the properties which are exhibited in its wood as a result 
of its life functions. Suppositions and conjectures more or less plausil)le preponderate over positive knowledge 
derived from exact observation and from the results of expiTiiuents. Still less comjiletc is our knowledge in regard 
to the relation of properties .and the methods and means used for shaping or working the wood. 

The close interrelation of all branches of natural science is now so well reciignized that I need not remind my 
readers that hard and fast lines can not be drawn whereby each field of inquiry is coulined and limited; there must 
necessarily be an overlapjiing from one to the other. Anj' system, therefore, of dividing a larger field of inquiry 
into parts is only a matter of convenience ; its divisions and correlations must be to some extent arliitrary and varied 
according to the point of view from which we proceed to divide and correlate. 

There are two definite and separate directions in which this branch of natural science needs to lie developed, 
and the knowledge comprised in it may be divided accordingly. On one side it draws its substance largely from the 
more comprehensive fields of botany, molecular physics, and chemistry, and on the other side it rests upon investi- 
gations of the wood material from the point of view of mechanics or dynamics. In the first direction we are led to 
deal with the wood material as it is, its nature or appearance and conditions; in the second direction we consider 
the wood material in relation to external mechanical forces, its behavior under stress. 

The first part is largely descriptive, concerned in examining gross and minute itructures, physical and chemical 
conditions and properties, and ultimately attempting to explain these by referring to causes and conditions which 
produce them. This is a field for investigation and research by the plant physiologist in tlu^ hiboratory in connec- 
tion with studies of environment in the forest. The second part, which relies for its development mainly upon 
experiment by th(^ engineer, deals with the properties which are a natural consequence of tin; structure, physii-al 
condition, and chemical composition of the wood as exhibited under the application of external mechanical forces. 
It comprises, th(^refore, those studies which contemplate the wood substance, with special reference to the uses of 
man, and forms ultimately tl^e basis for the mechanical technology of wood or the methods of its use in the arts. 

The correlation of the results of these two directions of study as cause and effect is the highest aim and 
ultimate goal, the philosophy of the science of timber physics. Timber ]>hj'sic8, in short, is to furnish all necessary 
knowledge of the rational application of wood in the arts, and at the 8aml^ time, by retrospection, such knowledge 
will enable us to produce in our owu forest growth qualities of given character. 



380 FORESTRY INVESTIGATIONS V. .s. DEPARTMENT UF A(iKI(;UI.TUKE. 

Conceived in this manner it becomes the pivotal science of the art of forestry, around whicli the practice both 
of the consumer ;ind producer of forest growth moves. 

The lirst part of our science would requiro a study into gross and miuute anatomy, the structure of the wood, 
foiui, dimensions, distribution, and arraniieineut of its cell elements and of groups of structural parts, not only in 
order to distiugnish the diHerent woods, but also to furnish the basis for an explanation of their physical and 
mechanical i)roperti<^s. WencxI would class here all investigations into the physical nature or properties of the 
wood material, which necessarily also involves an investigation into the change of these properties uiuler varying 
conditions and inlluences. A third chapter would occupy itself with tin- chemical composition and properties of 
woods and their changes in the natural process of life, which jiredicato the fuel value and dural)ility as well as the 
use of the wood in chemical technology. 

Although, philosophically speaking, it would hardly seem admissible to distinguish between physical and 
iiieclianical properties or to speak of " mechanical " forces, for the sake of convenience and practical purposes it is 
disiiable to make the distinction and to classify all phenomena and changes of nonliving bodies, or bodies without 
reference to life functions, into chemical, physical, and mechanical phenomeua and changes. As chemical phenomena 
or changes, and therefore also conditions or jiroperties, we class, then, those which have reference to atomic struc- 
ture; as physical phenomena, changes, and properties those which refer to and depend on molecular arrangement, 
and as mechanical (molar) changes and properties those which concern the masses of bodies, as exhibited under the 
inlluenco of external forces, without altering their physical or chemical {'onstitntion. 

There is no doubt that this division is somewhat forced, since not only most or all mechanical (as here conceived) 
changes are accompanied or preceded by certain alterations of the interior molecular arraugeiuent of the mass, but 
also many i>hysical phenomeua or properties, like density, weight, shrinkage, having reference to the mass, might 
lie classed as mechanical; yet if we conceive that physical phenomena are always concerned with the "<|uantity of 
matter in molecular arrangement" and with the changes produced by interior forces, while the latter are concerned 
lather with the "position of matter in nndecular arrangement " and with changes under application of exterior 
forces, the distinction assumes a practical value. 

Our conception of these distinctions will be aided if we refer to the physical laboratory as furnishing the 
evidence of physical phenomena and to the mechanical hiboratory as furnishing evidence of mechanical iiheuomena. 

These latter, then, form the subject of our second or dynamic part of timber physics, which cimcerns itself to 
ascertain mainly by experiment, called tests, under application of the laws of elasticity, the strength of the material 
and other properties which are exhibited as reactions to the influence of applied stresses, and those which need 
consiileralion in the mechanical use of the material in the various arts. 

Having investigated the material in its normal condition, we would necessarily come to a consideration of 
such physical and chemical conditions of the material as are abnormal and known as disease, decay, or defects. 

Finally, having determined the properties and their changes as exhibited in material produced under changing 
conditions or dift'ering in physical and structural respects, it would remain the crowning success and goal of this 
science to relate mechanical and physical properties with anatomical and physiological development of the wood 
substance. 

The subject-matter comprised in this branch of applied natural science, then, may be brought into the following 
schematic view : 

I. — Wood sirih'Tike ok xyi.otomv. 
(a) Exterior form. 

Here would be described the form development of timber in the standing tree, ditferentiated into root 
system, root collar, boh' or (runk crown, branches, twigs; relative amounts of material furnished by each. 
(h) Interior utruclural appearance; diti'ereutiation and arrangement of groups of structural elements. 

Here would be described the gross structural features of the wood, the distribution and size of medul- 
lary rays, vessels, fibro-vascnlar bundles, as exhibited to the naked eye or under the magnifying glass on 
tangential, radial, and transverse sections; the appearance of the annual rings, their size, regularity, dif- 
ferentiation into summer and spring wood, and all distinguishing features due to the arrangement and 
proportion of the tissues composing the wood. 
(c) Minute nnatomij or liistologij; diffcientiation and arrangement of structural elements. 

Here the revelations of the microscope are recorded, especially the form, dimensions, and structure of 
the ditVerent kinds of cells, their arrangement, proportion, and relative importance in the resulting tissues. 
{(i) Comparitlire elaanificaiion of woods, according to siriicliiral features. 
^c) Lawn of wood i/rowtk with reference to structural results. 

Discussion of the faitors that influence the formation of wood in the standing tree. 
(/) Abnormal forynationa. 

Burls, bird's eye, curly, wavy, and other structural abnormities and their causes. 
II. — I'liYsiCAi. I'ltorEUTlES, i. e., properties based on molecular ([ihysical) constitution. 
(a) Exterior appearanee. 

Such properties as can be observed through the unaided senses, as color, gloss, grain, texture, smell, 
resonance. 
(fc) yiaterial condition. 

Such properties or changes as are determined by measurements, as density or weight, water contents 
and their distribution, volume, and its changes by shrinkage and swelling. 



TIMBER PHYSICS — EARLIER WORK. 381 

(c) aa^sifcaiiov of u-oods according t., physico-iechnical properties, i. c, such physical properties as determine 
their application in the arts. 
III.— Chemical i-hoi'krties, i. e., properties based on atomic (chemical) constitution. 
(«w;,w»'ai e/.«»iica? aim/i/sis o/- »o«d (qualitative and quantitative). 

Here ^vould be discussed the chemical constitution of dirterent vvoods and difterent parts of trees and 
their changes due to physiological processes, age, conditions of growth, etc. 

(h) Carhohudrahx of the wood. . ■ , ^ i 4.i,„;, 

Here would he more specially discussed cellulose and lignin, .ork formations, organic contents and their 
changes, and such properties as predicate the fuel value of woods, their mannfactnre into charcoal, their 
food value, pulping qualities, et(\ 

(c) Exiractife material.i. ■ „ .,1 

A knowledge of these underlies the application of wood in the manufacture oi tan extrarts, res.n, and 

turpentine, tar, gas, alcohol, acids, vanillin, etc. 

(d) '^''*'2^^'^J^"^'^2T^ ;';. jj^^^^^ ehemical properties whi,-h predicate durability and underlie processes of increasing 

the same, 
fe^ Mineral consliliients, • , i.j. * 

A knowledge of the.^e in particnl.ar will establish the relation of wood growth to mineral constituents 
of the soil andllso serve .as basis for certain technical uses (potash). 
IV.-MEC..ANICAL ruoPERTlES, i. e., properties base.l on elastic conditions exhibite.l by the aggregate mass under 

influence of exterior (mechanical) forces, 
(a) /■ormc;m«flC8ir«/,OH<rfes(r»c(i»»<>/c»/'«si«», commonly culled elasticity, tlexib.hty. toughness. 
(A) Form chanflc, mtU de^lr,wlio« of cohesion, conunonly ,alled strength (tensile, eom,.ress.ve, torsional, shearing), 
cleavability, hardness. 
V.—Technical PROPERTIES, i. c., properties in combination. , . , ,, . ,■ ,■ • 41 „.t„ 

Here would be considered the woods with reference to their technical use, their application ,u the arts, 
which is invariably based upon a combination of several physical or mechanical properties. 

VI Diseases and faults. , . , , i-.- 

Here would be treated the changes in structure and properties from the normal to abnormal conditions, 
due to influences acting upon the tree during its life or upon the timber during its use. 
VII —Relation of propkhties to each other. , • , , 1 

Here would be discussed the connection which may be established between structure, physical, chemical 
.and mechanical i.roperties, and als.. between these and the conditions of growth under which the material 
was produced. The philosophy of the entire preceding knowledge would here be brought together. 
To contribute toward this important branch of human knowledge and to help in the building ol its foundation, 
the work undertaken by the Division of Forestry described in this bulletin was designed by the writer; and, in 
order to build with a kn'owledge of what has been done before on this structure, a brief review „t the progress ,n 
the development of timber physics seemed advisable. 

This historical review is then given. From this we deem it appropriate to quote the portion 
which refers to efforts in the United States up to the time of the writing to cstabhsh data 
regarding the mechanical properties of our timber: 

AMERICAN WORK. 

While it may bo possible to work out the general laws of relation between physical and mechanical properties 
on material of European origin, for practical purposes we can not rely upon any other data than those ascertained 
f 01 A 1 rican timb rs, and so .ar .as dependence of quality on conditions of growth are concerned this truth is.us 
as patent Although in the United States probably more timber has been and is being used than in any other 
country but little work has been done iu the domain of timber physics. •. , ti o ,.f 

An oiig the earliest American experiments falling in the domain of timber physics may be cited those of 
Marcus Bull to deteruune "the comparative quantities of heat evolved in the combustion of '^.'^ P""'"^! I'^"'"!! 
of wood and coal used in the United States for fuel," made in the years 1823 to 1825 and published in 18^6 H 
the experiments of Lavoisier, Crawford and Dalton, and Count Rumford on similar lines are discussed and followed 
by an able series of experiments and discussion on American woods and coals 

The only comprehensive work in timber physics ever undertaken on American timbers is that °"I'- T- P- 
Sharpies in conueition with the Tenth Census, and published in 1884, Vol. IX, on the Forests ot North America. 
?on p hen iveness, however, has been sought rather in trying to bring under examination all the arborescent species 
Snirnilhing fuller data of practical applicability on those from which the bulk of our useful material i 
IcHv d ''The results obtained," the author says, ".are highly suggestive; they must not, however, be eonsidered 
conclusive, but rather valuable as indicating what lines of research should be followed in a more thorough study oi 

""' NoiTess'than 412 species were examined in over 1,200 specimens. The results .are given in five tables, besides 
four comparative tabled of range, relative values, averages, etc. The specimens were taken " m most cases from 
the b °t7cut and free from sap and knots;" the locality and soil from which the tree came are given in most cases 
and in some its diameter an] layers of heart .and sapwood; determinations were made of specihc gravity, mineral 
ash per cent, and from these data fuel values were calculated. 



382 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 

Tlio spoiimeiis tested were "carernlly seasoned." For transverse straiu tliey were niailo 1 ccntimoters (1.57 
inches) siniare, and a i'ew of donblo lliese dimensions, with 1 meter (3.28 feet) span. 

One tabh> illnstrates " the relation between the specihe gravity and the transverse stren-^th of the wood of 
speeics, npon whieh a sufheient number of tests has been made to render suth a comparison valuable." This table 
seems to show that in perfect specimens weight and strength stand in close relation. A few tanning determinations 
on the bark of a few species are also given. 

The object of the work as stated, namely, to be suggestive of a more thorough study of the subject, has 
certainly been fully and creditably attained. Of compilatory works, for use in practice and for reference, the 
following, published in the United States, may be cited: 

Do Volson Wood: Resistance of Materials (1871), containing rather scanty references to the work of Chcvandier 
and'Wertheim. 

R. G. Hatfield: Theory of Transverse Strain (1877), which, besides other references, contains also twenty-three 
tables of the author's own test on white pine, Georgia pine, hemlock, spruce, white ash, and black locust, on sticks 
1 l)y I inch bv l.fi feet in length. 

William II. Burr: The Elasticity and Resistance of Materials of Engineering, third edition, 18110, a compre- 
hensive work, in whieh many relerenccs are made to the work of various American experimenters. 

Gaetano Lanza, in .\p|ilied Mechanics, 1885, lays especial stress on the fact that tests on small select pieces 
liive too high values, and quotes tlu' following experiments on Iimg jiieces. He rcd'ers to the work of Capt. T. .1. 
Rodman, United States Army, published in Ordnance Manual, who used test pieces '21 by 5| inches and :"> feet length, 
without giving any reference to density or other facts concerning the wood; and to Col. Laidley's United States 
Navy test (Senate Kx. Doc. lli. Forty-seventh Congress, first scission, 1881), who conducted a series of experiments on 
Pacific slope timbers, "white and' yellow pine," 12 feet long and 4 to 5 by 11 to 12 inches square, giving also 
account of density and average width of rings. 

Lastly, the author's own experiments, made at the Watertown Arsenal for the Boston Manufacturers' Mutual 
Fire Insurance Company, on the colunmar strength of " yellow pine" and white oak, 12 feet long and 6 to 10 inches 
thick, are brought in support of the claim that such tests show less than half the unit strength of those on small 
pieces. Data as to density, moisture, or life history of the specimens are everywhere lacking. 

R. H. Thurston, Materials of Engineering, 1882, contains, jierhaps, more than any other American work on the 
subject, devoting, in Chapters II and HI, 117 [lages to timber and its strength, and in the cha]itci' on Fuel several 
jiages to wood and charcoal, and the products of distillation. 'It .ilso gives a description of some twenty-five kinds 
of American anil of a few foreign timlier trees, with a descrijition of the structure .ind their wood in general; 
directions for felling and seasoning; discusses briefly shrinkage, characteristics of good timber, the induenco of 
.soil and climate on trees and their wood, and of the various tonus of decay of timlier, methods of preservation and 
adaptation of various woods for various uses, much in the same manner as Rankine's Manual of Civil Engineering 
from which many conclusions are adopted. The author refers, besides foreign authorities, to the following 
American investigators : 

G. H. Corliss (unpublished?) is quoted as claiming that proper seasoning of hickory wood increases its strength 
by 15 per cent. 

R. G. Hatfield is credited with some of the best experiments on shearing strength, published in the American 
House Carpenter. 

Prof. G. Lanza's experiments are largely reproduced, also Trautwine's on shearing, and some of the author's 
own work on California spruce, Oregon pine, and others, especially in torsiim, with a specially constructed machine, 
an interesting plate of strain diagrams accompanying the discussion. 

In connection with the discussion by the author on the influence of prolonged stress, there is quoted as one 
of the older investigators, Herman Haupt, whose results on yellow pine were published in 1871 (Bridge 
Construction). 

Experiments at the Stevens Institute of Technology are related, with the imiJortant conclusion that a load 
of GO per cent of the ultimate strength will break a stick if left loaded (one small test piece having liee.u left loaded 
fifteen mouths with this result). 

In addition the following list of references to American work in timber physics is here inserted, with a regret 
that it has not been possible to include all the stray notes which may be in existence but were not accessible. Those 
able to add further notes are invited to aid in making this reference list complete: 

Abbott, Arthur V. Testing machines, their history, construction, and use. With illustrations of machines, includ- 
ing that at Watertown Arsenal. Van Nostrand's Magazine, 1883, vol. 30, pj). 204, 325, 382. 477. 
Day, Frank M., University of Pennsylvania. The microscopic examination of timber with regard to its strength. 

Read before American Philosophical Society, 1883. 
Estrada, K. D. Experiments on the strength and other properties of Cuban woods. Investigations carried on in 
the laboratory of the Stevens Institute. Van Nostrand's Magazine, 188S, vol. 2S), pp. 417,441. 

Flint, . Report of tests of Nicaraguan woods. .Journal of Franklin Institute, October, 1887, pp. 289-315. 

(ioodale. Prof. George L., Harvard University. Physiidogical Botany, 1885, ch.aptcrs 1, 2, 3, 5, 8, 11, and 12. 
Ihlseng, JIagnus C, Ph. D. On the modulus of elasticity iu some American woods, determined by vibration. Van 
Nostrand's Magazine, 1878, 19. 

On a mode of measuring the velocity of sounds in woods. Read before the National Academy of Science, 

1877; published in American .Journal of Science and Arts, 1879, vol. 17. 
.Johnson, Thomas II. On the strength of columns. Paper read at annual convention of American Society of Civil 
Engineers, 1885. Transactions of the Society, vol. 15. 



TIMBEB PHYSICS — EARLIER WORK. 383 

Kidder, F. E. Exporimrnts at Maine State College on transverse strength of southern and white pine. Van Nostrand's 

Magazine, 1879, vol. 22. 

Experiments' with yellow and white pine. Van Nostrand's Magazine, 1880, vol. 23. 

Experiments on the strength .and stittness of small spruce beams. Van Nostrand's Magazine, 1880, vol. 24. 

Influence of time on bending strength and elasticity. Journal of Fr.auklin Institute, 1882. Proceedings 

Institute of Civil Engineering, vol. 71. 
Lanza, Gaetano, professor Massachusetts Institute of Technology. Address before American Society of Mechanical 

Engineers, describing the 50,000 pound testing machine at VVatertown Arsenal and tests of strength of large 

spruce beams. Journal of Friinkliu Institute, 1883. 
Report of Hoston Manufacturers' Mutual Fire Insurance Company of tests made with Watertown machine 

on columns of pine, whitewood, and oak of dimensions used in cotton .and woolen mills. See summary and 

tables of sami- in Burr's Elasticity and Resistance of the Materials of Engineering, p. 480. 
Macdonald, Charles. Necessity of government aid in making tests of materials for structural purposes. Paper re.ad 

before the American Institute of Mining Engineers. Van Nostrand's Magazine, 1882, vol. 27, p. 177. 
Norton Prof. \V. A., Yale College. Results of experiments on the set of bars of wood, iron, and steel after a 

transverse set. Experiments discussed in two papers read before the National Academy <d' Science, 1874 and 

1875. Published in Van Nostrand's Magazine, 1887, vol. 17, p. 531. 

Description of machine used is given in proceeilings of the A. A. A. S., eighteenth meeting, 18i;!l. 

Parker, Lieut. Col. F. II.. United States Orduance Department. Report of tests of American wnods by the testing 

machine. United States Arsenal, Watertown, under supervision of Prof. C. S. Sargent, for the Cen.sus Report, 

1880. Seuiite Ex. Doc. No. 5, Forty-eighth Congress, lirst session, 1882-83. 
Report of experiments on the adhesion of nails, spikes, and screws in various woods, as made at Watertown 

Arsenal. Senate Ex. Uoc. No. 35, Forty-ninth Congress, first session, 1883-84, and in report on tests of metals 

and other materials for industrial purposes at Watertown Arsenal, 1888-89. 
Also in report on tests of iron, steel, and other materials for industrial purposes at Watertown Arsenal, 

1886-87, pp. 188, 189. 

Report on cubic compression of various woods, as shown by tests at Watertown Arsenal, 188.5-86, in report 



on tests of metals, etc., for industrial pnrpi>ses. 
Philbrick. Professor, Iowa University. New practical formulas for the resistance of solid and built beams, girders, 

etc., with problems and designs. Van Nostrand's Magazine, 1886, vol. 35. 
Pike, Prof. W. A. Tests of white pine, made in the testing laboratory of the University of Minn<-sota. Van Nos- 
trand's Magazine. 1885, vol. 34, p. 472. 
Rothrock, Prof. . I. T.,Uuiver8ity of Pennsylvania. Some microscopic distinctions between good and bad timber of 

the same species. Read before American Philosophic Society. 
Smith, C. Shaler, C. E. Summary of results of 1,200 tests of full-size yellow-pine columns. See W. H. Burr's 

Elasticity and Resistance of the Materials of Engineering, pp. 485-490. 
Thurston, Prof. R. H., Cornell University. The torsional resistance of materials. Journal of Franklin Institute, 

1873, vol. 65. 

Experiments on torsion. Van Nostrand's Magazine, July, 1873. 

Experiments on the strength, elasticity, ductility, etc., of materials, as shown by a new testing machine. 

Van Nostrand's Magazine, 1874, v(d. 10. 
. The relation of ultimate resistance to tension and torsion. Proceedings of Institute of Civil Engineers, 

vol. 7, 1878. 
. The strength of American timber. Experiments at Stevens Institute. Paper before A. A. A. S., 1879. 

Journal of Franklin Institute, vol. 78, 1879. 
. Effect of prolonged stress upon the strength and elasticity of pine timber. Journal of Franklin Institute. 

vol. 80, 1880. 
. Influence of time on bending strength and elasticity. Proceedings A. A. A. S., 1881. Proceedings Institute 



of Civil Engineers, vol. 71. 
Watertown Arsenal. Summary of results of tests of timber at, in Ex. Doc. No. 1, Forty-seventh Congre.ss, second 

session. See Burr's Elasticity and Resistance of Materials of Engineering, pp. 486 and 535. 
Wellington, A. M., c. e. Experiments on impregnated timber. Railroad Gazette, 1880. 

OEGANIZATION AND METHODS. 

Although in the course of the investigations many minor and some more important changes 
in methods became necessary, the general plan -was in the main adhered to. We consider it, 
therefore, desirable to restate from the same bulletin such portions as will explaiu the methods 
pursued. The work at the test laboratory at St. Louis, Mo., was described in full by Prof. J. B. 
Johnson, in charge, and the metbods in the examination of the physical properties of the test 
material by the writer. 

There are four departments necessary to carry on the work as at present organized, namely : 

(1) The collecting department. 

(2) The department of mechanical tests. 



384 FORESTRY INVESTKiATIONS U. S. DEPARTMENT OF AGRICULTURE. 

(3) Tbe department of physical and microscopic examination of the test material. 

(4) The department of compilation and final discnssion of results. 

The region of botanical distribution of any one speoics that is to be investigated is divided 
into as many stations as there seem to be widely different climatic or geological differences in its 
habitat. In each station are selected as many sites as there seem widely different soils, elevations, 
exposures, or other stiiking conditions occupied by the species. An expert collector describes 
carefully the conditions of station and site, under instructions and on blanks appended to this 
report. From each site five mature trees of any one species are chosen, four of which are average 
representatives of the general growth, the fifth, or "check" tree, the best developed that can be 
found. The trees are felled and cut into logs of merchantable size, and from the butt end of each 
log a disk inches in height is sawed. Logs and disks are marked with numbers to indicate 
number of tree and number of log or disk, and their north and south sides are marked ; their height 
in tiie tree from the ground is noted in the record. The disks are also weighed immediately, then 
wrapped in oiled paper and packing paper, and sent by mail or express to the laboratory, to serve 
the ijurpose of physical and structuial examination. Some disks of the limbwood and of younger 
trees are also collected for other physical and physiological investigations, and to serve with the 
disks of the older trees in studying the rate of growth and otlier problems. 

The logs are shipped to the test laboratory, there sawed and i>repared for testing, carefully 
marked, and tested for strength. 

The fact that tests on large pieces give different values from those obtained from small pieces 
being fully established, a number of large sticks of each species and site will be tested full length 
in order to establish a ratio between the values obtained from the different sizes. Part of the 
material is tested green, another part when seasoned by various methods. Finally, tests which 
are to determine other working qualities of the various timbers, such as ada])t them to various 
uses, are contemplated 

The disks cut from each log and correspondingly marked are examined at the botanical labora- 
tory. An endless amount of weighings, measurings, countings, computings, microscopic examina- 
tions, and drawings is required here, and recording of the observed facts in such a nninner that 
they can be handled. Chemical investigations have also been begun in the Division of Chemistry 
of the Department of Agriculture, the tannic contents of the woods, their distribution through the 
tree and their lelation to the conditions of growth forming the first seiies of these investigations. 

It is evident that in these investigations, can ied on by competent observers, besides the main 
object of the work, much new and valuable knowledge unsought for must come to light if the 
investigations are carried on systematically and in the comprehensive plan laid out. Since every 
stick and every disk is marked in such a manner that its absolute position in the tree and almost 
the absolute position of the tree itself or at least its general condition and surroundings are known 
and recorded, this collection will be one of the must valuable working collections ever made, allo.w- 
iug later investigators to verify or extend the studies. 

This significant prophetic language also occurs in this connection, which has finally been 
realized by the discovery of the relation between compression and beani strength: 

I3y mid liy it is expected that the luimljer of tests uecessary may Ije reduced considerably, when for eacli species 
tlie relation of the different exhibitions ofstrengtli can be sufficiently established, and ]ierhaps a test for compres- 
sion alone furnish sufficient data to compute the strength in other directions. 

WORK AT TIIE TEST LABORATORY AT ST. LOUIS, MO. 
SAWING, STOniNG, AND SEASONING. 

On arrival of the logs in St. Louis they are sent to a sawmill and cut into sticks, as shown in fig. 103. 

In all cases the arrangements shown in Nos. 1 and 2 are used, except when a detailed study of the timber in all 
parts of the cross section of the log is intended. A few of the most perfect logs of each species are cut up into small 
sticks, as shown in Nos. 3 and 1. The logs tested for determining the effects of extracting the turpentine from the 
Southern pitch jjines were all cut into small sticks. 

In all cases a "small stick" is nouiiually 4 inches square, but when dressed down for testing may be as small as 
3i inches si|Uiire. The "large sticks" vary from 6 by 12 to 8 by 16 inches iu cross section. 

All logs vary from 12 to IS feet in length. They all have a north and south diametral line, together with the 
numlier of the tree and of the log plainly marked on their larger or lower ends. The stenciled lines for sawing are 



TIMBER PHYSICS — TESTING. 



385 



adjusted to this north and soiith line, as sliowu in the figures. Each space is then branded liy deep dies with three 

25 

numbers, as, for instance, thus ; ', which signifies that this sticli was number 4, in log 2, of tree 2.5. A facsimile of 

4 

the stenciling is recorded in the log book, and the sticks there numbered to correspond with the numbering on the 
logs. After sawing, each stick can be idcntilied and its exact origin determined. These three numbers, then, become 
the idoutificatiou marks for all 8|>ecimeus cut from this stick, and they accompany the results of tests in all the 
records. 

The methods of sawing .shown in Nos. 2 and 4 are called "boxing the heart;" that is, all the heart portion is 
thrown into one small stick, which in practice may be thrown away or put into a lower grade without serious loss. 
In important bridge, floor, or roof timbers, the heart should always be either excluded or " boxed" in this way, since 
its presence leads to ebeclving and impairs the strength of the stick. 

.\rter sawing, the timbers are stored in the laboratory until they are tested. The "greeu tests" are made 
usually within two months after sawing, while the "dry tests" are made at various subsequent times. One end 
((iO inches) of each small stick is tested green, and the other end reserved and te-sted after seasoning. The seasoning 
is hastened in some cases by means of a drying box. The temperature of the inflowing air in this drying box is 
kept at about 100 ' F., with suitable precaution against checking of the wood, and the air is exhausted by means of 
a fnn. The air is, therefore, somewhat rarefied in the box. The temperature is at all times under control. It 
operates when the fan is running, and this is only during working hours. 

The mechanical and moisture te>st are then made according to known methods. 




Jf 




/ 


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' i 


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Y 






\ 








v\ 












/ 


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Fio. 10.3. — Method of sawing test logs. 
EXAMINATION INTO THE PHYSICAL PROPBETIES OF TEST MATERIAL. 

The phy.sical examination consists in ascertaining the specific weight of the dried material, 
and incidentally the progress and amount of shrinkage due to seasoning; the counting and 
measuring of the annual rings, and noting other microscopic appearances in the growth; the 
microscopic investigation into the relation of spring and summer wood from ring to ring; the 
frequency and size of medullary rays; the ^.imber of cells and thickness of their walls; and, in 
short, the consideration of any and all elements which may elucidate the structure and may have 
influence upon the properties of the test iiiece. The rate of growth and other biological facts 
which may lead to the finding of relation between physical appearance, conditions of growth, and 
mechanical properties are also studied incidentally, 

SHAPING AND MARKING OF THE MATERIAL. 

The object of this work being in part the discovery of the differences that exist in the wood, not 
only in trees of different species or of the same species from various localities, but even in the wood 
of the same tree and from the same cross section, a careful marking of each piece is necessary. The 
disks are split, first into a north and south piece, and each of these into smaller pieces of variable 
size. In one tree all pieces were made but 3 cm. thick radially, in another 4 cm., in still others 5 cm., 
while in some trees, especially wide-ringed oaks, the pieces were left still larger. In the conifers 
the outer or first piece was made to contain only sap wood. Desirable as it appeared to have each 
piece contain a certain number of rings, and thus to represent a fixed period of growth, it proved 
impracticable, at least in the very narrow-nnged disks of the pines, where sometimes the width of 
a ring is less than 5 mm. (0.2 inch). 
H. Doc. 181 25 



38G 



FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



Some of the disks were split to a wedge sliape from center to periphery, so that each smaller 
piece not only represents a certain period of growth in quality, but also in quantity, thus simplify- 
ing the cal(;ulations for the entire piece or disk. Other pieces were left in their i)rismatic form, 
when to calculate the average density of the entire piece the density of eavAi smaHer piece is 
multiplied by the mean distance of this smaller piece from the center, and the sum of the products 
divided by the sum of the distances. 

Each piece is marked, first by the number of the tree, in Arabic; second, by the number of 
the disk, in Komau numbers; and if split into small pieces, each smaller piece by a letter of the 
alphabet, the piece at the periphery in all cases bearing the letter a. Besides the number and 
letters mentioned, each piece bears either the letter N or S, to indicate its orientation on the north 
or south side of the tree. To illustrate: 5 — vii N a means that the piece bearing the label 
belongs to tree 5 and disk vii comes from the north side of the tree, and is the peripheral part of 
this disk piece. From the collector's notes the exact position of this i>iece in the tree can readily 
be ascertiiined. 

The entire prisms sent by Ireight are left in the original form, unless used for special purposes, 
and are stored iu a dry room for future use. 

WEIfilllNG AND MEASURING. 

The weighing is done on an apothecary's balance, readily sensitive to 0.1 gram with a load of 
more than 200 grams. Dealing with pieces of iJO(» to 1,000 grams in weight, the accuracy of weigh- 
ing is always within 1 gram. 

The measuring is done by immersion iu an instrument illustrated in the following design: I'is 
a vessel of iron ; »S' represents one of two iron standards attached to the vessel and i)rq)ectiug 




Fio. 1(14. — Apitiiratiis lor ilntenniniiig apt'citid gravity 



above its top; B is a metal bar fastened to the cup A, which serves as guard to the cup and pre- 
vents it going down farther at one time than another by coming to rest on the standards S. The 
cup A dips down one-sixteenth to one-eighth of an inch below the edge of the knee-like spout. In 
working, the cup is lifted out by the handle which the bar B forms, water is poured into the vessel 
until it overflows through the spout, (hen the cup is set down, replacing the mobile and fickle 
natural water level by a constant artificial one. Now the instrument is set, the pan 1' is placed 
under the spout, the cup is lifted out and. held over the vessel, so that the drippings fall back into 
the latter, the piece of wood to be measured is put into the vessel and the cnp replaced, antl pressed 
down until the bar /> I'ests on the staud;irds <S'. This is done gently to ])rev»'nt the water from rising 
above the rim of the vessel. This latter precaution is superfluo us where the eiip fits closely, as it 



TIMBER PHYSICS PHYSICAL EXAMINATION. 68 t 

does ill one of tlie instruiiients thus far used. The pan with water is then weighed, the pan itself 
being- tared by a bag of sliot. Tlie water is poured out, the i)an wiped dry, and the process begins 
anew. To work well it takes two persons, one to weigh and record. The water pan is a seamless 
tin pan, holding about 1,500 cc. of water and weighing only 144 grams. The temperature as well 
as density of the water are ascertained, the hitter, of course, omitted when distilled water is used. 
To maintain the water at the same temperature it requires frequent changing. 



After marking, the jiieces are left to dry at ordinary temperature. Then they are placed in a 
dry kiln and dried at lOO"^ 0. 

The drying box, used is a double-walled sheet-iron case, lined with asbestus paper, and heated 
with gasoline. The air enters below and has two outlets on top. The temperature is indicated by 
a thermometer and maintained fairly constant. 

After being dried, the pieces of wood are weighed and measured, in the same way as described 
for the fresh wood, and from the data thus gathered the density, shrinkage, and moisture per cent 
are derived in the usual manner. 

The formuliB employed are : 

M. T^ ,(. *• ^--^^i „„„,! Weight of fresh wood. 

(1 Density or tresh wood = ^^ , " t.-„— , ^,- 

Volume 01 fresh wood. 

,o\ r« •* .■ 1 1 Weight of dry wood. 

(2) Density ot dry wood = ^^ , =■ ,. , 

Volume 01 dry wood. 

,.,, r,, • , Fresh volume — dry volume. 

(3) tehnnkage= = = = — ^ 

Fresh volume. 

, , > T,!^ • . • , Fresh weight — dry weight. 

1 4) Moisture in wood = rs-^, -■-,-, — 

Fresh weight. 

Tn presenting these values they are always multiidied by 100, so that the density expresses 

the weight of 100 cm.^ of wood; thus the shrinkage and the amount of moisture become the 

shrinkage and moisture jter cent. 

.SHRINKAOE EXPEUniF.NTS. 

To discover more fully the relations of weight, humidity, and shrinkage, as well as "checking" 
or cracking of the wood, a number of separate experiments were made. A number of the fresh 
specimens were weighed and measured at variable intervals until perfectly dry. Some dry pieces 
were placed in water and kept immersed until the maximum voluiu.e was attained. Without 
describing more in detail these tests and their results, it may be mentioned that in the immersed 
jjieces studied the liiial maximum volume differed very little, in some cases not at all, from the 
original volume of the wood when I'resh; and also that in a piece of white pine only 15 en;, long 
and weighing but 97 gs. when dry, it required a week before the swelling ceased. 

To determine the shrinkage in different directions a number of measurements are made in 
pieces ot various sizes and shapes. In most cases pins were driven into the wood to furnish a lirm 
metal point of contact for the caliper. A number of pieces of oak were cut in various ways to 
study the etlect ot size, form, and relative position of the graiu ou checking. 

WOOD STRUCTURK. 

The most time-robbing, but also the most fascinating, part of the work consists in the 
study ol the wood as an important tissue of a living organism; a tissue where all favorable and 
unfavorable changes experienced by the tree during its long lifetime find a permanent record. 

GKNERAL APPEARANCE. 

For this study all the specimens from one tree are brought together and arranged in the same 
order in which they occurred in the tree. This furnishes a general view of the appearance of the 
stem; any striking peculiarities, such as great eccentricity of growth, unusual color, abundance 
of resin in any part of the stem, are seen at a glance and are noted down. 

A table is prepared with separate columns, indicating — 

(1) Height ot the disk in the tree (this being furnished by the collector's notes); 

(2) Radius of the section ; 



388 POKESTRY INVKSTIGATIONS TT. S. DEPARTMENT OF AGRICULTUEE. 

(3) Niimlxir of rings from perijjliery to center; 

(4) Number of rings in the sapwood; 

(5) Width of the sapwood; and 
(0) Kemarks on color, grain, etc. 

The results from each disk occupy two lines, one for the i)ieces from the north side and one 
for those of the south side. The radius is measured correct to one-half millimeter (0.02 iiuih), and 
the figures refer to the air-dry wood. 

To couut tlie rings, the piece is smoothed witli a sharp knife or jjlane, th(> cut being made 
oblique, i. e., not quite across the grain, nor yet longitudinal. Beginning at the periphery, each ring 
is marked with a dot of ink, and each tenth one with a line to distinguish it from the rest. After 
counting, the rings are measured in groui)s of ten, twenty, thirty, rarely more, and these meas- 
urements entered in separate subcolumns. In this way the rate of growth of the last ten, twenty, 
or thirty years throughout the tree is found, also that of similar periods jjrevious to the last; in 
short, a fairly complete history of the rate of growth of tlie tree from the time when it had reached 
the height of the stump to the day when felled is thus obtained. Not only do tliese rings furnish 
information concerning the gi-owth in thickness, but indicating the age of the tree when it had 
grown to the height, from which the second, third, etc., disks were taken, tlie rate of growth in 
height, as well as that of thickness, is deterndned, any unfavorable season of growth or any series 
of such seasons are found faithfully recorded in these rings, and tlie influence of such seasons, 
whatever their cause, both on the (|uantitj^ and on the (juality or properties of the wood, can thus 
be ascertained. 

In many cases, especially in the specimens from the longleaf pine, and from the limbs of all 
pines, the study of these rings is somewhat diflScult. Zojies of a centimeter and more exist where 
the width of the lings is such that the magnifier has to be used to distinguish them. In some cases 
this difficulty is increased by the fact that the last cells of one year's growth differ from the first 
cells of the nest year's ring oidy in form and not in the thickness of their walls, and therefore 
jiroduce the same color effect. Such cases frequently occur in the wood of the upper half of the 
disks from limbs (the limb supported horizontally and in its natural position), andoften tlie magnifier 
has to be reenforced by the microscope to furnish the desired information. For this puri)osc the 
wood is treated as in all microscopic work, being first soaked in water and then sectioned with a 
sharp knife or razor and examined on the usual slide in water or glycerin. 

The reason for beginning the counting of rings at the periphery is the same which suggested 
the marking of all periplieral pieces by the letter a. It is convenient, almost essential, to have, 
for instance, the thirty-fifth ring in Section II represent the same year's growth as thethirty-flfth 
ring in Section X. The width of the sapwood, the number of annual rings composing it, as well 
as the clearness and uniformity of the line separating tlie sapwood from the heartwood, are 
carefully recorded. In the columns of " remarks" any peculiarities which distinguish the particular 
piece of wood, such as defects of any kind, the presence of knots, abundance of resin, nature of 
the grain, etc., are set down. 

When finished, a variable number, commonly :i to (5 small pieces, fairly representing the wood 
of the tree, are split off, marked with the numbers of their respective disks, and set aside for the 
microscopic study, which is to tell us of the cell itself, the very element of structure, and of its 
share in all the properties of wood. 

The small pieces are soaked in water, cut with a sharp knife or razor, and examined in water, 
glycerin, or chloriodide of zinc. The relative amount of the thick-walled, dark-colored bands of 
summer wood, the resin ducts, the dimensions of the common tracheids and their walls, both in 
spring and summer wood, the medullary rays, their distribution and their elements, are the 
principal subjects in dealing with coniferous woods; the (luantitative distribution of tissues, or 
how much space is occupied by the thick-walled bast, how much by ves.sels, how much by thin- 
walled, pitted tracheids and parenchyma, and how much by the medullary rays; what is the 
relative value of each as a strength-giving element; what is the space occupied by the lumina, 
what by the cell walls in each of these tissues — these are among the important points in the study 
of the oaks. 

Continued sections from center to periphery, magnified 25 diameters, are employed in finding 
the relative amount of the summer wood ; the limits of the entire ring and that of spring and 



TIMBER PHYSICS STATEMENT OF RESULTS. 



3«y 



M.W.68 



v.. 57 

K .■35;-. 
S.11% 




m 

18 



\S.6.9% 
lW..73Ttv.Tn~ 



\S. 97. 
llW:.7Sm.m. 



245mjn\D..64 

Aw. 317, 
. 9.4% 




lS2m.m. V.53 
FT. W- 3«% 



V.Sl 
W337. 

s.s.ez 

R.W.Sim-m.. 



191jnrm^V0 .57 

fr7I63W>iGsW-33X 

\s.iox 

LH.TK.Mm.T. 



175m.m. S..59 

FT. ~W33Z 



W.'337.tiBe_ ^JSKl 




,D..e4 

FT. B29/liNes\s.W.'9tn.m. 
£W.43% 



D.X 

ir.iozlsr 90 

5. 7.67.1 
H.W.T 



1)..36 

.S-. 7.2-: 
jnr.73 




.34 

r!.67W3SZ 
S.6.Z% 
njn^.59m.Tn. 



...38 
FT. lis \W.40Z 
"•■"'■ I.S.7.3% 

.W..79m.m. 



J74/IINes \D..3e 
FT.W.™.„1^38% 

wr.777n.?n. 



J>..Jlf 

140% 
S. 7.9Z 
R.W.gSmm. 



D..37 
W347. 
,S.9.7% 
liW.83m.yn. 



ilS^I>i«eS_ YD .39 
FT. 207m.77t. "K^^^t 

Tr.9Jnt.7n. 

.43 
'39~. 
S.9.4Z 
iJf.IT. 977n.iit. 



t97RlNes\D..4-t 

FT. 180m.m7\R^W-91m.m. 



Fig. 105 Result of physit-al examination. (Sample.) 



LoNULKAF I'LNE (P. jmbislris), trees. 
Locality : Wallace, Ala. 
Site: Uplaml forest, iiiiito iloiiso. 
Soil: Saiiiiy. 



White pine {P. Strubas), tree 116. 
Localitii : Maratlion County, Wis. 
Sitt:: Grown in elun.sc iiii.Ked forest. 
Soil: Sandy, with sandy subsoil. 



Legend. 



D. Denotes density or .spccitic gravity of the dry wood. 

W. Denotes percentage of water in the fresh wood, related to its 

weight. 
5. Denotes percentjige of jhriukage in liiln drying. 
li. W. Denotes width of ring (average) inmiUimcters (25mm. = l inch). 
S. W. Denotes percentage of summer wood as related to total wood. 
Koman numbers refer to number of disk, placed in iio.sition of disl^. 



Height is given in feet from tho ground ; scale, 10 feet= 2 inches. 
Radius, north and south (dotted line), in millimeter.s ; scale, 10 mm. = 

0.1 inch. 
Median line represents the pith. 
Right-hand numbers relate to north side, left-hand numbers to south 

sid''. 
Outer lines represent outlines of trees. 



390 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 

suiumer wood are marked on paper with the aid of the camera, and thus a panorama of the entire 
section is brought before the eye. Tlie liistology of the wood, the resin ducts, the tracheids and 
medullary rays, their form and dimensions, are studied in thin sections magnified 580 diameters 
and even more. Any peculiarity in form or arrangement is drawn with the camera and thus 
graphi(;ally recorded; the dimensions are measured in the manner described for the measurement 
of the summer wood, or with the ocular micrometer. In measuring cell walls the entire distance 
between two neighboring luinina is taken as a "double wall,'' the thickness of the wall of either of 
the two cells being one-half of this. Tlie advantage of this way of measuring is ai)parent, since 
the two points to be marked are in all cases perfectly clear and no arl)itrary positions involved. 
The length of the cells is found in the usual way l)y se])arating the elements with Schultze's 
solution (nitric acid, chlorate of potassium). All results tabulated are averages of not less than 
ten, often of more than one hundred, measurements. 

In the attempt to find the quantitative relations of the different tissues, as well as the density 
of each tissue, various ways have been followed. In some cases drawings of magnified sections 
were made on good, even paper, the different parts cut out, and the paper weighed. In other cases 
numerous measurements and computations were resorted to. Though none of the results of these 
attempts can be regarded as perfectly reliable, they have done much to point out the relative 
importance of different constituents of the wood structure, and also the possibility and practica- 
bility, and even the necessity, of this line of investigation. 

INSTRUCTIONS AND BLANK FORMS, WJTH ILLUSTRATIVE RECORDS. 
Instructions fok the Collection ok Test Pieces ok Pines for Timber Investioations. 

A. — ohject ok work. 

The collector fhould undcrst.and that the ultimate object of these investigations is, if possible, to establish the 
relation of fjiiality of timber to the couditious under which it is grown. To accomi)li8h this object he is expected 
to furnish a very careful description of the conditions under which the test trees have grown, from which test pieces 
are taken. Care in ascertaining these and minuteness and accuracy of description are all-important in assuring 
proper results. It is also necessary to select and prepare the test pieces esactlj' as described and to make the records 
perl'ect as nearly as possible, since the history of the material is of as much importance as the determination in the 
laboratory. 

Ji. — localities for collecting. 

As to the locality from which test trees are to be taken, a distinction is niade into station and site. 

By station is to be understood a section of country (or any jilaces within that section) which is characterized 
in a general way by similar climatic conditions and geological formaticm. "Station," then, refers to the general 
Geographical situation. "Site" refers to the local conditions and surroundings within the station from which test 
trees are selected. 

For example, the drift deposits of the Gulf Coast jilain may be taken fur one station; the liuiestono country of 
northern Alabama for a second. But a limestone formation in West Virginia, which differs climatically, would 
ni^eessitate another station. Within the first station a rich, moist hummock may furnish one site, a sandy piece of 
upland another, and a wet savannah a third. Within the second or third station a valley might furni.sh one site, 
the top of a hill another, a different exposure may call for a third, a drift-capped ledge with deeper soil may wan-ant 
the selection of another. 

Choice iif stations . — For each species a special selection of stations from Avhich test pieces are to be collected is 
necessary. Those will be determined, in each case separately .as to number and location, from this otHce. It is 
proposed to cover the field of geographical distribution of a given species in such a manner as to take in stations 
of climatic difference and different geological horizon, neglecting, however, for the present, stations from extreme 
limits of distribution. Another factor which will determine choice is character of soil, as dependent upon geological 
formations. Stati(ms which promise a variety of sites will be preferably chosen. 

Choice of site. — Such sites will be chosen at each station as are usually occupied by the species at any one of 
the stations. If unusual sites are found occupied by the species at any one of the stations it will be determined by 
special correspondence whether test pieces are to be collected from it. The determination of the numlier of sites at 
each station must be left to the .judgment of the collector after inspection of the localities; but before determining 
the number of sites the reasons for their selection must be reported to this office. The sites are characterized and 
selected by ditl'erences of elevation, exposure, soil conditions, and forest conditions. The difference of elevation 
which may distinguish a site is provisionally set at .500 feet; that is, with elevation as the criterion for choice of 
stations the difference must be at least 500 feet. Where differences of exposure occur a site .should be chosen on 
each of the exposures present, keeping as much as possible at the same elevation and under other similar conditicms. 
Soil conditions may vary in a number of directions, in mineral composition, pliysical properties, depth, and nature 
of the sntisoil. For the present, only extreme differences in depth or in moisture conditions (drainage) and decided 
dillerence in mineral compoBition will be considered in making selection of sites. 



TIMBER PHYSICS 00LI.ECTIN(3 MATERIAL. 301 

Forest e(in<litions icfcr, in the first pLace, to mixed or pure forest, open or close stand, and should be chosen as 
near as possible to the normal character prevailins; in the region. If what, in the judgment of the colloctor, consti- 
tutes normal conditions are not found, the history of the forest and the points wherein it difl'ers from normal 
conditions must be specially noted. 

C. — CHOICE OF TRKES. 

On each site five trees are to be taken, one of which is to serve as "check tree." None of these trees .are to be 
taken from the roadside or open lield, nor from the outskirts, bu^ all from the interior of the forest. They are to be 
representative average trees — neither the largest or best nor the smallest or worst, preferably old trees and such as 
are not overtopped by neighbors. 

The "check tree," however, should bo selected with special care, and should represent the best-developed tree 
, that can be found, judged by relative height and diameter development and perfect crown. 

The distance between the selected trees is to be not less than 100 feet or thereabout, yet care must be exercised 
that all are found under precisely the same conditions for which the site was chosen. 

There are also to be taken six young trees as prescribed under E. 

If to be had within the station, select two trees from 80 to 60 years old or older, which are known to have 
grown up in the open, and two trees which are known to have grown up in the forest, but have been isolated for a 
known time of ten to twenty years. 

D. — PROCKDURE AND OUITIT. 

The station determined upon, the collector will proceed to examine it for the selection of sites. After having 
selected the sites, he will at once communicate the selection, with description and justification, to this office, 
negotiate with the owners of the timber (which might be done conditionally during the first examination) for the 
purchase or donation of test trees; and the latter arrangements completed, without waiting reply from this office, 
he will at once proceed to collect test pieces on one of the sites in regard to the selection of which he is not in doubt. 

To properly carry out the instructions, the following assistants and outfit may be reciuired: 

(1) Two men' with ax and saw; a boy also may be of use. 

(2) Team, wagon, and log trucks for moving tost pieces and logs to station. 

(3) Frow or sharp hacking knife for splitting disks. Heavy mallet or medium-sized "maul" to be u.sed with 
frow. 

(4) A handsaw. 

(5) Red chalk for marking. (A special marking hammer will be substituted.) 

(6) Tape line and 2-foot rule or calipers. 

(7) Tags (specially furnished). 

(8) Tacks (12-ounce) to fasten tags. 

(9) Wrapping jiaper and twiue. 

(10) Franks for mailing test pieces (specially furnished). 

(11) Shipping tags for logs. 

(12) Scales, with weight jiower not less than 30 pounds. 

(13) Barometer for ascertaining elevations. 

(14) Compass to ascertain exposures. 

(15) Spade and pick to ascertain soil conditions. 

(16) Bags for shipping disks. 

B. — mi:thoi> of making test pieces. 

(a) Mature trees. 

(1) Before felling the tree, blaze and mark the north side. 

(2) Fell tree with the saw as near the ground as practicable, avoiding the flare of the butt and making the 
usual kerf with the ax opposite to the saw, if possible, so as to avoid north and south side. If necessary, square 
off the butt end. 

(3) Before cutting off the butt log mark the north side on the second, third, and further log lengths. 

(4) Measure off and cut logs of merchantable length .and diameters, beginning from the butt, noting the length 
and diameters in the record. 

Should knots or other imperfections, externally visible, occur within 8 inches of the log mark, make the cut 
lower down or higher up to avoid the imperfection. 

(5) Continue measuring the full length of the tree and record its length. Note also distance from the ground 
and position on the tree (whether to the north, south, west, east) of one large sound limb. Mark its lower side and 
saw it of!;' close to the trunk and measure its length and record it, the limb to be utilized as described later. 

If the tree after felling prove unsound at the butt, it will he permissible to cut off as much or as little as 
necessary within the first log length. If sound timber is not found in the first log, the tree must be discarded. 
Only sound timber must be shipped. Any logs showing imperfections may be shortened. Be careful to note change 
in position of test pieces. 

(6) Mark butt end of each log with a large N on north side. Saw off squarely from the bottom end of each log 
a disk 6 inches long, and beyond the log measure cut off disks every 10 feet up to 2-inch diameter. Place eack disk 



' Only men familiar witU felling and cutting tiniber should be chosen, 



392 



FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



on its bottom end, and after having ascertainL-d and niarl<od the north and south line on to]i i^nd. Split the disk 
with a sharj) hacking knife and mallet along this line. Split from outside of the west half of the disk enough wood 
to leavea prism 1 imhes tliick. Split from the east half two wedges with one plane in this south-north Iin(^ and with 
their wedge line llirough the lieart of the disk ; the outer arc to he about 1 inches. 

Mark each piece as split off ou top side with number of the tree (Arabic), the serial number (Roman) of the 
disk in the tree, beginning with No. 1 al butt log, aud with a distinct N or S, the north oi- south position of the 
piece as iu the tree. 

Write the same data ou a card .ind tack it to the i)i(^ce to which they belong. Whenevtr disk piocis are small 
enough for mailing, leave them entire. Whenever they can not be shipped by mail, leave disks entire, wrap iu paper, 
aud ship by express. 

(7) Weigh each piece aud record weight iu notebook, using the same marks as appear on the i>ioces. 

(8) AVrap each piece in two sheets of heavy wrapping paper aud tie securely. 

(9) Mark on the newly cut bottom end of each log with a heavy pencil a north and south line, writing N on 
the north aud S on the south side of the log, large and distinct. Also mark centrally with an Arabic nuTubcr on 
each log the number of the tree in the series, and with a distinct Roman number the serial unmber of the log in the 
tree, counting the butt log as first. ^ 

Tack to the butt end of each log securely a card (centrally), on which is written name of tree, species, ioiality 
from which tree is taken, denoted by the letter coircspondiug to that used iu the notebook, number of tree, aud 
section. This card or tag is intended to insure a record of each log iu addition to the marking already made. 

(10) Limb wood. — Having, as before noted, selected a limb, measured and recorded its <listance from the butt 
aud position on the trunk, and marked its lower side and sawed it off dose to the latter, now take a disk G inches 
long from the butt end aud others every 5 feet up to 2-inch diameter at the top. Number tliese consecutively with 
Roman number, calling the butt disk No. 1. Note by letters L and II the lower aud upper side, as the limb appeared 
on the tree, and place the (Arabic) number of tree from which the limb came on each. Enforce the record by cards 
contaiuiug the same information, as done in case of other disk pieces. 

Weigh and wrap aud mail in the same manner as the other pieces. 

(11) Check trees. — From the "check tree," which is to be the very best to be found, only three disks or three 
logs are to be secured, from the butt, middle, and top part of the tree Absolutely clear timber, free from all knots 
aud blemishes, is to bo chosen. The disk pieces are to be of the same size, and to be secured in the same Uianner as 
those described before; the logs to bo not necessarily more than 6 feet; less if not enough clear timber can be found. 

Note the position of each piece 
iu the tree by measuring from the butt 
cut to the butt end of the piece. 

r'repare and mark all pieces iu 
the sauu; manner as those from other 
trees, adding, however, to each piece 
a X mark to denote it as coming from 
the "check tree." 

(12) yomuj trees.— Select six trees 
from each site approximately of fol- 
lowing sizes: Two, fi-iuch diameter, 
breast high; two, 4-iuch diameter, 
breast high; two, 2-inch diameter, 
breast high. Mark north and south 
sides and chop or saw all close to the 
ground aud cut each tree into following lengths: First stick, 2 feet long; second stick, 4 feet long; the remaining 
cuts 4 feet long up to a top end diameter of about 1 inch. Cut from the basal end of each log a disk C inches long. 
JIark and ticket butt end of each log as in case of large trees. Mark a north and south line on to}/ end of each 
disk, with N and S at extremities to denote north and south sides; and also ticket with same data as given on 
large disk pieces. Weigh and wrap as before. Of these trees only the disk pieces are to be mailed. 

F. — SHIPPING TEST PIECES. 

Ship all pieces without delay. To each log tack securely a shipping card (furnished), so as to cover the markiug 
tag. The logs will go to J. B. Johnson, St. Louis, Mo. The disks aud other pieces are to be mailed to F. Roth, Ann 
Arbor, Mich., using franks, securely pasted, for uuiiling, unless, as noted before, they must be sent by express. 

Mail at once to the above addresses notice of each shipment, and a transcript of notes and full description to 
this office, from which cojiies will be forwarded to the recipients of the test pieces. 

If free transportation is obtained from the railroad companies, special additional instructions will be given 
under this head. 

G. — KECOKDS. 

Careful and accurate records are most essential to secure the success of this work. A set of specially prepared 
record sheets will be furnished, with instructions for their use. A transcript of the record must be sent to this office 
at the time of making shii>ment; also such notes as may seem desirable to complete the record and to give additioual 
explanations in regard to the record and suggestions respecting the work of collecting. Original records aud notes 
must be jjreserved, to avoid loss iu transmission by mail. 






TIMBER PHYSICS — COLLECTING MATEUIAL. 



393 



FORM OF FIELD RECORD. 

(Folder.) 

Name of crtllector: (Charles Mohr.) Kpecios: Pinus palustria. 

Station (denoted by capital letter): A. 

State: Alabama. County: Escambia. Town: Wallace. 

Longitude: 86' 12'. Latitude: 31° 15'. Average altitude: 75 to 100 feet. 

General configuration : Plain— hills— plateau — mouutainous. General trend of valleys or hills 

Climatic features: Subtropical; mean annual temperature, 65°; mean annual rainfall, 62 inches. 
Site (denoted by small letter) : a. 

Aspect: Level— ravine — cove— bench — slope (angle approximately). 

Exposure: Elevation (above average station altitude): 125 feot. 

Soil conditions : 

(1) Geological formation (if known): Southern stratified drift. 

(2) Mineral composition: Clay— limestone— loam— marl— sandy loam— loamy sand — sand. 

(3) Surface cover : Bare— grassy — mossy. Leaf cover: AJbnmlant— scanty— lacking. 

(4) Depth of vegetable mold (humus): Absent — moderate— plenty— or give depth in inches. 

(5) Grain, consistency, and admixtures: Very line— fine— medium — coarse— porous— light — loose- 

moderately loose — compact — binding — stones or rock, size of 



(6) Moisture conditions: Wet— moist— fresh— dry— arid— well drained — liable to overflow— swampy — near 

stream or spring or other kind of water supply.. 

(7) Color: Ashy-gray. 

(8) Depth to subsoil (if known) : .Shallow, 3 to 4 inches to 1 foot— 1 foot (o 4 feet, deep— over 4 feet, very 

deep^shiftiug. 

(9) Nature of subsoil (if ascertainable) : Red, ferruginous sandy loam ; moderately loose, or rather slightly 

binding; always of some degree of dampness; of great depth. 

Forest conditions: Mixed timber — pure — dense growth — moderately dense to open 

Associated species: None. 

Projioi'tious of these 

Average height: 90 feet. 

Undergrowth: Scanty; in the original forest often none. 
Conditions in tlio open: Field — pasture — lawn — clearing (how long cleared): In natural clearings untouched 
by tire, dense groves of second growth of the species. 
Nature of soil cover (if any) : Weeds — brush — sod. 



Station: A. 



(Inside of folder.) 
Site: a. Species: P. palustris. TiiEE No. 3. 



Position of tree (if :iny special point notable not ajipearing in general descriptiou of site, exceptional exposure to 

light or dense position, etc., protected by buildings, note on back of sheet) : In rather dense positiou. 
Origin of tree (if ascertainable) : Natural seedling, sprout from stump, artificial planting. 



DiAMETEi: breast high: 16 inches. 
Height to iirst limb: 53 feet. 
Age (annual rings on stump) : 183. 



Height of stump: 20 inches. 

Length of felled tree: 110 feet 4 iuches. 

Total height: 111 feet 8 inches. 



No. of disk. 


Diat-iiice 
from butt. 


Weiffht of 

(-■ombined 

disk pieces. 


Ecmarks. 


No. of log. 


Bistance 
from butt. 


Length of 
log. 


Diameter, 
butt end. 


I 


Feet. 

13 
19 
32 
47 
57 
67 
77 
87 
97 


Pounds. 

27 
20 
20 
18 
16 
14 
17 
14 


Crown to\ichins those 
of nearest trees to the 
N. and NE. Open 
toward SW. 


I 

11 

Ill 

IV 

V 

VI 

VII 

VUI 


Ft. In. 
8 0. 
13 8 
19 8 
32 S 
47 8 

r>7 8 

67 8 
77 8 


P(. In. 

12 4 
5 4 

12 4 

14 4 
9 4 
9 4 
9 4 
9 4 


Inches. 
16J 

13i 
121 
'U 


II 


Ill 


IV 


V 


VI 


VII 


VIII 


IX 


X 





LiMBWOOD : 

Distance from butt: 
Number of disks taken: 



Position on trunk : 



Total length: 



Note. — As much as possible make description by underscoring terms used above. Add other descriptive terms 
if necessary. 



394 



FOKESTUY INVESTIGATIONS U. S. PEPARTRrENT OF AGKICULTURE. 



SAMPLE RECORDS OK TESTS. 



CKO.S.S BREAKING TKST. 



(116. 

Mark, 1. 
1 3. 

1.0Df;tli, fiO.O inches. 
Ileiglit, 3.74 iiichos. 
lireadtb, 3.75 inches. 



Wliito pino. 



Streuf^th of extreme fiber, 
S TV I 
where /:=^.-p=. 5,600 ponntls per Bqnare inch. 

Modulus of (dastii'.ity =l,;i2ll,()0(i iiiiiinils per si|iia.reinch. 
Total nisiliiuce ^3,160 inch-i)oiiu(l8. El. Kcs., 550. 

Resilience, per cubic inch ^4.11 inch-pounds. El. Res., 0.65. 



[Nninber annnal rings per inch =19.] 



Jul.V 18, 
1891. 


Load. 


Deflection. 


Micrometer. 


Remarks. 


h. m. 

4 24 
25 
26 
27 
28 
29 
31 
33 
35 
37 
40 


.200 
1,000 
l.COO 
2, 000 
2, 200 
2, 400 
2,600 

2, 8110 
3,000 
3,20(1 

3, 300 


.042 
.211 
.300 
.454 
.511 
.595 
.600 
.8.53 
1.015 
1.276 
1.521 


0.757 
0. 926 
1.065 
1.169 
1.226 
1.310 
1.405 
1.5C8 
1. 730 

1. 991 

2. 238 




i 










Maximum lo.ad. 






Jfeflectian, in, iruChes. 



TIMBER PHYSICS METHODS. 



395 



CROSS BREAKING TKST. 



f3. 



Longle;if piue. 



Mark, 3. 
11. 

Length, 60.0 iiicUes. 
Height, 3.50 inches. 
Breadth, 3.72 inches. 



[Number annual rings per inch=23.] 



gOOO | 



strength of extreme fiber; 

where /'=o ,-,^^^10,230 pounds per squan^ inch. 

Modulus of elasticity =1,760,000 pounds per8i|uare inch. 
Total nsilience =.^,110iu< li-punnds. El. Res., 1,7H0. 

Resilience, per cubic inch ^6.34 inch-pounds. El. Res., 2.28. 



July 
20,1891. Load. 



2 58 I 200 

3 I 1,000 

1 I 1,600 

2 , 2,000 

3 2,400 

4 2, 800 

5 3, 200 

6 3, UOO 

7 4, 000 

8 4,400 

9 4, 800 
13 I 5,180 



Deflec- 


Micro- 


tion. 


meter. 


.042 


0. S.'iS 


.208 


1.124 


.324 


1.240 


.401 


1.320 


.481 


1.397 


. 5.-.8 


1.474 


.t>40 


1.556 


.721 


1.637 


.815 


1. 731 


.926 


1.842 


1.074 


1.990 


1.544 


2.460 




Mark. 



Lougloaf pine: 

3 

3 

1 

"Wliilo pine; 

116 

1 

3 



Mark. 



Longlcaf piue: 

3 

3 

1 

"W'liitc pine; 

116 

1 

3 



Mark. 



Longleaf pine : 

3 

3 

1 

White piue; 

116 

1 

3 



Deflection in inches, 

FINAL UECOED OB' TIMBER TESTS. 



Percent- 
age of 
moiHture 



16.8 



Cross bending test. 



Dimensions. 



Length. 



Inckcg. 
60.0 



Height. 



Inches. 
3.50 



3.74 



Broadtli. 



Inches. 
3.72 



3.75 



Min. 
15 



Load. 



Pounds. 
5,180 



Deflec- 
tion. 



Inches. 
1,544 



1, 521 



Strength 

per 

square 

inch. (/) 



Pounds. 
10, 230 



5,660 



Modulus 
of elas- 
ticity, (fi) 



Pounds. 

1, 760, 000 



Resilience 
in incli- 

pouudspel 

cubic 

inch, (r) 



Crushing endwise. 



Crushing across grain. 



Dimensions. 



Height. 



Inches. 
8.1 



7.6 



Cross 
section. 



Inches. 

3.46 
3.72 



3.73 
3.73 



Crushing 
load. 



Sq. in. 
\ 12.87 



} 13.91 



Pounds. 

77, 700 



48, 400 



Strength 

per 

square 

inch. 



Pounds. 
6,040 



3,480 



Dimensions. 



Height. 



Inches. 
3.73 



Cross 
section. 



Inches. 

3.47 
3.93 



3.72 
3.93 



Crushing 
load. 



Sq. inch, 
\ 13.63 



Pounds. 
10, 400 



5,200 



Strength 
per square 



Tension testa. 



Size of re- 
duced sec- 
tion. 



Sq.inch. 

2.38 
.41 



Area. 



Sq. inch. 
\ 0. 976 



2.53 
.45 



Breaking 
load. 



Pounds. 
11, 400 



Strength 

per square 

inch. 



Pounds. 
11,680 '( 



Shearing tests. 



Total 

shearing 

,nrea. 



Sq. inch. 
4.14 
3.97 



1,880 j| 



4.16 
4.02 



Bre.akiug 
load. 



Pounds. 

2,280 
2.580 



1,700 
1,600 



Sliearing 
strength. 



Pounds. 



551 
650 



400 
398 



p.u'nq 



